Biomedical subjects

M Kelley

Publications and source records attributed to M Kelley.

At least 37 records · Page 2Linked to original sources

PubMed2000

APRIL and TALL-I and receptors BCMA and TACI: system for regulating humoral immunity.

We report that the tumor neurosis factor homolog APRIL (a proliferation-inducing ligand) stimulates in vitro proliferation of primary B and T cells and increases spleen weight due to accumulation of B cells in vivo. APRIL functions via binding to BCMA (B cell maturation antigen) and TACI (transmembrane activator and CAML-interactor) and competes with TALL-I (also called BLyS or BAFF) for receptor binding. Soluble BCMA and TACI specifically prevent binding of APRIL and block APRIL-stimulated proliferation of primary B cells. BCMA-Fc also inhibits production of antibodies against keyhole limpet hemocyanin and Pneumovax in mice, indicating that APRIL and/or TALL-I signaling via BCMA and/or TACI are required for generation of humoral immunity. Thus, APRIL-TALL-I and BCMA-TACI form a two ligands-two receptors pathway involved in stimulation of B and T cell function.

Animals↗

PubMed2000

Characterization of osteoclast precursors in human blood.

Osteoclast precursors (OCPs) circulate in the mononuclear fraction of peripheral blood (PB), but their abundance and surface characteristics are unknown. Previous studies suggest that the receptor activator for NF-kappaB (RANK) on cytokine-treated OCPs in mouse bone marrow interacts with osteoprotegerin ligand (OPGL/TRANCE/RANKL/ODF) to initiate osteoclast differentiation. Hence, we used a fluorescent form of human OPGL (Hu-OPGL-F) to identify possible RANK-expressing OCPs in untreated peripheral blood mononuclear cells (PBMCs) using fluorescence-activated cell sorting analysis. Monocytes [CD14-phycoerythrin (PE) antibody (Ab) positive (+) cells, 10-15% of PBMCs] all (98-100%) co-labelled with Hu-OPGL-F (n > 18). T lymphocytes (CD3-PE Ab+ cells, 66% of PBMCs) did not bind Hu-OPGL-F; however, B cells (CD19-PE Ab+ cells, 9% of PBMCs) were also positive for Hu-OPGL-F. All Hu-OPGL-F+ monocytes also co-labelled with CD33, CD61, CD11b, CD38, CD45 and CD54 Abs, but not CD34 or CD56 Abs. Hu-OPGL-F binding was dose dependent and competed with excess Hu-OPGL. When Hu-OPGL-F+, CD14-PE Ab+, CD33-PE Ab+, Hu-OPGL-F+/CD14-PE Ab+ or Hu-OPGL-F+/CD33-PE Ab+ cells were cultured with OPGL (20 ng/ml) and colony-stimulating factor (CSF)-1 (25 ng/ml), OC-like cells readily developed. Thus, all freshly isolated monocytes demonstrate displaceable Hu-OPGL-F binding, suggesting the presence of RANK on OCPs in PB; also, OCPs within a purified PB monocyte population form osteoclast-like cells in the complete absence of other cell types in OPGL and CSF-1 containing medium.

B-Lymphocytes↗

PubMed2000

A pilot study of neoadjuvant paclitaxel and radiation with correlative molecular studies in stage II/III breast cancer.

A commonly used approach to the management of locally advanced breast cancer currently involves neoadjuvant chemotherapy, followed by surgery and radiation. Earlier neoadjuvant regimens had utilized doxorubicin, making concurrent treatment with radiation less desirable given dose-limiting normal tissue toxicities. With the development of paclitaxel, we can now reconsider the use of concurrent chemoradiation in the treatment of breast cancer. Although paclitaxel is a known radiation sensitizer, its precise mechanism of action is still unclear. One of its proposed mechanisms is that it binds tubulin and induces an M-phase arrest. As cells in M-phase are very sensitive to radiation, it thereby increases radiation sensitivity. The ability to predict tumor response for individual patients would allow us to tailor subsequent therapy for the individual patient. This study is designed to evaluate if paclitaxel's effects on the cell cycle of an individual patient can predict the responsiveness of that patient's tumor to paclitaxel and radiation. Patients will be treated with 3 cycles of paclitaxel followed by concurrent paclitaxel and radiation prior to definitive surgery.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Management of rotator cuff and impingement injuries in the athlete.

OBJECTIVE: To review current concepts of the pathophysiology, diagnosis, and treatment of rotator cuff and impingement injuries in the athlete. DATA SOURCES: The information we present was compiled from a review of classic and recently published material regarding rotator cuff and impingement injuries. These materials were identified through a search of a personal literature database compiled by the authors, as well as by selective searching of the MEDLINE. In addition, much of the information presented represents observations and opinions of the authors developed over 8 to 10 years of treating shoulder injuries in athletes. DATA SYNTHESIS: Biomechanics of the normal shoulder and pathophysiology of rotator cuff injuries in the athletic population are discussed, followed by a summary of the important diagnostic features of rotator cuff and impingement injuries. The principles of rehabilitation are extensively presented, along with indications and important technical aspects of selected surgical procedures. General principles and specific protocols of postoperative rehabilitation are also summarized. CONCLUSIONS/RECOMMENDATIONS: Rotator cuff and impingement injuries in the athletic population are multifactorial in etiology, exhibiting significant overlap with glenohumeral instability. Nonoperative treatment is successful in most athletic patients with rotator cuff and impingement injuries. When nonoperative treatment fails, arthroscopic surgical techniques such as rotator cuff repair and subacromial decompression may be successful in returning the athlete to competition.

Journal Article↗

PubMed1999

Characterization of the CoA ligases of human liver mitochondria catalyzing the activation of short- and medium-chain fatty acids and xenobiotic carboxylic acids.

Two distinct forms of xenobiotic/medium-chain fatty acid:CoA ligase (XM-ligase) were isolated from human liver mitochondria. They were referred to as HXM-A and HXM-B based on their order of elution from a DEAE-cellulose column. Activity of the two ligases was determined toward 15 different carboxylic acids. HXM-A represented 60-80% of the benzoate activity in the lysate, and kinetic analysis revealed that benzoate was the best substrate (highest V(max)/K(m)). The enzyme also had medium-chain fatty acid:CoA ligase activity. HXM-B had the majority of the hexanoate activity and hexanoate was its best substrate. It was, however, also active toward many xenobiotic carboxylic acids. Comparison of these two human XM-ligases with the previously characterized bovine XM-ligases indicated that they were kinetically distinct. When assayed with benzoic acid as substrate, both HXM-A and HXM-B had an absolute dependence on either Mg(2+) or Mn(2+) for activity. Further, addition of monovalent cation (K(+), Rb(+), or NH(4)(+)) stimulated HXM-A activity by >30-fold and HXM-B activity by 4-fold. For both forms, activity toward straight-chain fatty acids was stimulated less by K(+) than was activity toward benzoate or phenylacetate. A 60 kDa short-chain fatty acid:CoA ligase was also isolated. It had activity toward propionate and butyrate, but not acetate, hexanoate or benzoate. The K(m)(app) values were high but similar for propionate and butyrate (285 microM and 250 microM, respectively) but the V(max)(app) was nearly 6-fold greater with propionate as substrate. While the K(m) values are somewhat high, the enzyme is still more efficient with these substrates than either of the XM-ligases.

Animals↗

PubMed1999

Modified-peptide inhibitors of amyloid beta-peptide polymerization.

Cellular toxicity resulting from nucleation-dependent polymerization of amyloid beta-peptide (Abeta) is considered to be a major and possibly the primary component of Alzheimer's disease (AD). Inhibition of Abeta polymerization has thus been identified as a target for the development of therapeutic agents for the treatment of AD. The intrinsic affinity of Abeta for itself suggested that Abeta-specific interactions could be adapted to the development of compounds that would bind to Abeta and prevent it from polymerizing. Abeta-derived peptides of fifteen residues were found to be inhibitory of Abeta polymerization. The activity of these peptides was subsequently enhanced through modification of their amino termini with specific organic reagents. Additional series of compounds prepared to probe structural requirements for activity allowed reduction of the size of the inhibitors and optimization of the Abeta-derived peptide portion to afford a lead compound, cholyl-Leu-Val-Phe-Phe-Ala-OH (PPI-368), with potent polymerization inhibitory activity but limited biochemical stability. The corresponding all-D-amino acyl analogue peptide acid (PPI-433) and amide (PPI-457) retained inhibitory activity and were both stable in monkey cerebrospinal fluid for 24 h.

Amino Acid Sequence↗

PubMed1999

The ligand for osteoprotegerin (OPGL) directly activates mature osteoclasts.

Osteoprotegerin (OPG) and OPG-ligand (OPGL) potently inhibit and stimulate, respectively, osteoclast differentiation (Simonet, W.S., D.L. Lacey, C.R. Dunstan, M. Kelley, M.-S. Chang, R. Luethy, H.Q. Nguyen, S. Wooden, L. Bennett, T. Boone, et al. 1997. Cell. 89:309-319; Lacey, D.L., E. Timms, H.-L. Tan, M.J. Kelley, C.R. Dunstan, T. Burgess, R. Elliott, A. Colombero, G. Elliott, S. Scully, et al. 1998. Cell. 93: 165-176), but their effects on mature osteoclasts are not well understood. Using primary cultures of rat osteoclasts on bone slices, we find that OPGL causes approximately sevenfold increase in total bone surface erosion. By scanning electron microscopy, OPGL-treated osteoclasts generate more clusters of lacunae on bone suggesting that multiple, spatially associated cycles of resorption have occurred. However, the size of individual resorption events are unchanged by OPGL treatment. Mechanistically, OPGL binds specifically to mature OCs and rapidly (within 30 min) induces actin ring formation; a marked cytoskeletal rearrangement that necessarily precedes bone resorption. Furthermore, we show that antibodies raised against the OPGL receptor, RANK, also induce actin ring formation. OPGL-treated mice exhibit increases in blood ionized Ca++ within 1 h after injections, consistent with immediate OC activation in vivo. Finally, we find that OPG blocks OPGL's effects on both actin ring formation and bone resorption. Together, these findings indicate that, in addition to their effects on OC precursors, OPGL and OPG have profound and direct effects on mature OCs and indicate that the OC receptor, RANK, mediates OPGL's effects.

Actins↗

PubMed1999

Osteoprotegerin and osteoprotegerin ligand effects on osteoclast formation from human peripheral blood mononuclear cell precursors.

Osteoprotegerin (OPG) and its ligand (OPGL) negatively and positively regulate osteoclastogenesis in the mouse. OPG inhibits osteoclastogenesis by sequestering its ligand, OPGL, the osteoclast differentiation and activation factor. This study demonstrates the effects of soluble muOPGL and huOPG on the developing human osteoclast phenotype, on bone slices, using peripheral blood mononuclear cells (PBMCs), cultured for 2 weeks, without stromal cells. OPGL (2-50 ng/ml), in combination with CSF-1, hydrocortisone (HC), and 1,25(OH)2D3, increases the size of osteoclast-like cells on bone, as defined by the acquisition of osteoclast markers: vitronectin receptor (VR), tartrate-resistant acid phosphatase (TRAP), multinuclearity, and bone resorption. By 14 days, with 20 ng/ml OPGL, the largest cells/10x field have achieved an average diameter of 163+/-38 microm, but only approximately 10-20 microm in its absence and the number of osteoclast-like cells/mm2 bone surface is about 128. By scanning electron microscopy, OPGL-treated (20-ng/ml) cultures contain small osteoclast-like cells on bone with ruffled "apical" surfaces by day 7; by day 15, large osteoclast-like cells are spread over resorption lacunae. At 15 ng/ml OPGL, about 37% of the bone slice area is covered by resorption lacunae. OPG (5-250 ng/ml) antagonizes the effects of OPGL on the morphology of the osteoclast-like cells that form, as well as bone erosion. For cells grown on plastic, Cathepsin K mRNA levels, which are barely detectable at plating, are elevated 7-fold, by 5 days, in the presence, not the absence, of OPGL (20 ng/ml) + CSF-1 (25 ng/ml). Similar findings are observed in experiments performed in the absence of HC and 1,25(OH)2D3, indicating that HC and 1,25(OH)2D3 are not needed for OPGL-induced osteoclast differentiation. In conclusion, this study confirms a pivotal role for OPGL and OPG in the modulation of human osteoclast differentiation and function, suggesting a use for OPG for treating osteoclast-mediated bone disease in humans.

Animals↗

PubMed1999

Comparison of blue dye and probe-assisted intraoperative lymphatic mapping in melanoma to identify sentinel nodes in 100 lymphatic basins.

OBJECTIVE: To determine whether combining isosulfan blue dye with a radiopharmaceutical agent will increase intraoperative detection of sentinel nodes (SNs) in patients with early-stage melanoma. PATIENTS AND DESIGN: Clinical trial with a consecutive sample. Eighty-seven patients with clinical stage I melanoma underwent preoperative lymphoscintigraphy with 1 of 3 radiopharmaceutical agents to identify the lymphatic basin and the site of the SN. All patients subsequently underwent intraoperative lymphatic mapping and selective lymph node dissection (SLND) with isosulfan blue dye and a radiopharmaceutical agent. A handheld gamma probe determined the radioactive counts over the draining lymph node basins and individual blue-stained lymph nodes before (in vivo) and after (ex vivo) their removal. An irrelevant body site was used as the denominator of a count ratio by which absolute counts were standardized for comparison. Completion lymphadenectomy was undertaken in patients whose SLND specimen had histopathologic evidence of tumor cells. SETTING: Tertiary care cancer center. INTERVENTION: Lymph node sampling. MAIN OUTCOME MEASURE: Accuracy of SN detection by blue dye and radiopharmaceutical techniques. RESULTS: Preoperative lymphoscintigraphic images identified 100 lymph node basins and 135 lymph nodes in 87 patients. All 3 radiopharmaceutical agents were equally effective in imaging the SN before surgery. During SLND, we identified and removed 136 blue-stained and radioactive (hot) SNs and 8 additional non-blue-stained hot nodes from 98 basins (98.0%). Of the 144 excised lymph nodes, 132 nodes (91.7%) from 83 basins had either an in vivo- or an ex vivo-background count ratio of 2:1 or more and 125 nodes (86.8%) from 77 basins had a count ratio of 3:1 or more. Twelve blue-stained SNs had count ratios of less than 2:1. Seventeen SNs (11.8%) from 15 basins contained metastases: 16 were identified with blue dye and probe and 1 was identified with blue dye alone. Four (1.1%) of 377 non-SNs excised during completion lymphadenectomy contained metastases. There have been no lymph node recurrences during mean follow-up of 16.3 months (range, 7-42 months). CONCLUSIONS: The blue dye technique remains the criterion standard for SLND in melanoma. The addition of a radiopharmaceutical tracer serves as a useful adjunct to the visualization of blue-stained SNs.

Female↗

PubMed1999

Downsizing, reengineering and patient safety: numbers, newness and resultant risk.

Downsizing and reengineering are facts of life in contemporary healthcare organizations. In most instances, these organizational changes are undertaken in an attempt to increase productivity or cut operational costs with results measured in these terms. Less often considered are potential detrimental effects on patient safety or strategies, which might be used to minimize these risks.

Hospital Restructuring↗

PubMed1999

Methodologic drift in the assessment of TIMI grade 3 flow and its implications with respect to the reporting of angiographic trial results. The TIMI Study Group.

BACKGROUND: The Thrombolysis in Myocardial Infarction (TIMI) Study Group originally defined TIMI grade 3 flow (complete perfusion) as antegrade flow into the bed distal to the obstruction that occurs as promptly as antegrade flow into the bed proximal to the obstruction. Recently, several groups have defined TIMI grade 3 flow as opacification of the coronary artery within 3 cardiac cycles. METHODS AND RESULTS: On the basis of heart rate data at the time of the cardiac catheterization and the time for dye to go down the artery (TIMI frame count/30 = seconds), we estimated the number of patients who would meet the 3 cardiac cycle criterion and compared this with the number of patients with TIMI grade 3 flow by using the original definition in 1157 patients from 3 recent TIMI trials (10 A, 10B, and 14). In 74 patients without acute myocardial infarction and normal coronary arteries, the fraction of a cardiac cycle required for dye to traverse the artery was a mean of 0.93 +/- 0.34 cardiac cycles (n = 74) (median 0.80, minimum 0.44, maximum 2.1, none >3.0 cycles). The mean heart rate at 90 minutes after thrombolysis in the TIMI 14 trial was 79.6 +/- 16.8 beats/min (n = 194), and the duration of 3 cardiac cycles was a mean of 2.36 seconds, or a TIMI frame count of 70.8 frames. In all trials, the rate of TIMI grade 3 flow was 57.3% (n = 663/1157) with the original definition and 66.8% (n = 743/1113) with the <3 cardiac cycle definition (P <.001). CONCLUSIONS: A duration of 3 cardiac cycles for dye to traverse the artery lies approximately 6 SD above that observed in normal coronary arteries. A 3 cardiac cycle definition of TIMI grade 3 flow results in rates of normal perfusion that are approximately 10% higher than if the original definition of TIMI grade 3 flow is applied. Application of this simple correction factor may help place data reported with the 3 cardiac cycle definition of TIMI grade 3 flow in context.

Cineangiography↗

PubMed1999

Angiographic methods to assess human coronary angiogenesis.

It is unclear how agents designed to promote angiogenesis in the human heart affect the arteriographic appearance of the collateral circulation. Possible changes in collateral vessels include new collateral vessels arising from epicardial arteries, new branches emanating from existing collateral vessels, wider or longer collateral vessels, and higher dye transit rates that result in improved recipient vessel filling. Given the multiple mechanisms by which these new agents may improve myocardial perfusion, a rigorous, systematic, and comprehensive analysis of coronary arteriograms is required to discern the true mechanism of benefit. The method of analysis must account for potential changes in collateral blood flow, number, branching pattern, and length as well as changes in recipient vessel filling. The ability to detect differences between intricate networks of vessels in an angiographic study is dependent on maintaining consistency in cinefilming as well as the core laboratory methods between time points. In this report, we describe the methodology our angiographic core laboratory has found to be most effective to evaluate these very complex angiograms and attempt to capture all the possible modalities of angiogenesis.

Collateral Circulation↗

PubMed1999

Communication about sexual issues: mothers, fathers, and friends.

PURPOSE: To identify the content, characteristics, and comfort level of discussions about sexuality held between mothers and their early adolescent children and to determine the extent to which the conversations predicted sexual values and initiation of sexual intercourse of the adolescent. METHODS: This was part of a larger study to evaluate the impact of personal family characteristics on human immunodeficiency virus risk-reduction behavior among low-income predominately African-American adolescents, ages 13-15 years. Adolescents attending a metropolitan community-based afterschool program and their mothers were invited to participate in a 1-hour interview. Mothers and adolescents were interviewed separately. The interview included questions about the type of information related to sexuality that adolescents discussed with mothers, fathers, and friends; in addition, mothers were asked what topics they discussed with their adolescents. Four hundred five adolescents and 382 mothers participated. Some mothers had more than one adolescent in the study. RESULTS: The results showed that both male and female adolescents were more likely to discuss sexual topics with their mothers than their fathers. Male adolescents were more likely than female adolescents to discuss sex-based topics with their fathers. Both male and female adolescents were less likely to discuss sex-based topics with their friends than with their mothers, but more likely to discuss these topics with their friends than their fathers. Content of conversations of male adolescents was fairly consistent among mothers, fathers, and friends, and sexually transmitted disease/acquired immune deficiency syndrome and condom use were popular topics of discussion. Female adolescents tended to talk about the menstrual cycle with their mothers, sexual abstinence with their fathers, and sexual intercourse with their friends. Adolescents who reported a greater number of topics discussed with their mothers were more likely not to have initiated sexual intercourse and to have conservative values, whereas adolescents who reported a greater number of topics discussed with their friends were more likely to report the initiation of intercourse and more "liberal" sexual values. Both male and female adolescents were most comfortable discussing sexual issues with their friends. Male adolescents were less comfortable talking to mothers, but more comfortable talking to their fathers than were females. Mothers were likely to report feeling very comfortable talking about almost all discussion areas. Fathers' comfort level was not measured, as they were not directly questioned. CONCLUSION: Early adolescence (13-15 years old) is characterized by more sex-based discussions with mothers than friends or fathers. Daughters and sons discuss different topics with their fathers, although discussion by both genders with fathers is limited. If an adolescent talks more with the mother about sexual issues than with friends, he/she is less likely to initiate sexual intercourse and more likely to have conservative values. This points to the importance of fostering good communication and comfort between parents and adolescents about sexual issues.

Adolescent↗

PubMed1999

Ebola (subtype Reston) virus among quarantined nonhuman primates recently imported from the Philippines to the United States.

In April 1996, laboratory testing of imported nonhuman primates (as mandated by quarantine regulations) identified 2 cynomolgus macaques (Macaca fascicularis) infected with Ebola (subtype Reston) virus in a US-registered quarantine facility. The animals were part of a shipment of 100 nonhuman primates recently imported from the Philippines. Two additional infected animals, who were thought to be in the incubation phase, were identified among the remaining 48 animals in the affected quarantine room. The other 50 macaques, who had been held in a separate isolation room, remained asymptomatic, and none of these animals seroconverted during an extended quarantine period. Due to the rigorous routine safety precautions, the facility personnel had no unprotected exposures and remained asymptomatic, and no one seroconverted. The mandatory quarantine and laboratory testing requirements, put in place after the original Reston outbreak in 1989-1990, were effective for detecting and containing Ebola virus infection in newly imported nonhuman primates and minimizing potential human transmission.

Animals↗

PubMed1999

Intravenous midazolam for sedation of children undergoing procedures: an analysis of age- and procedure-related factors.

OBJECTIVE: This study was performed to determine the doses of midazolam used for sedation during procedures in children, and the frequency of adverse events. METHODS: We performed a retrospective analysis of data collected for a prospective study of flumazenil in children who had received midazolam for a procedure (n = 91, 1-17 years). RESULTS: Practitioners used a wide range of total midazolam doses (0.03-0.6 mg/kg); mean doses ranged from 0.09 +/- 0.06 mg/kg in adolescents to 0.26 +/- 0.13 mg/kg in toddlers (P < 0.001). Opioids were also used in 84% of patients. Twenty-six percent of children with normal lungs, most of whom had received relatively high opioid doses, developed decreased oxygen saturation (as low as 65%) after sedation. Other adverse events included airway obstruction (n = 3) and vomiting (n = 1). CONCLUSIONS: The frequent choice of midazolam, usually combined with an opioid, indicates its wide acceptance. Midazolam doses were inversely related to age. The presence of vomiting, airway obstruction, and decreased oxygen saturation underlines the importance of appropriate personnel, equipment, and monitors during sedation.

Adolescent↗

PubMed1999

Evidence from molecular fingerprinting of limited spread of drug-resistant tuberculosis in Texas.

To determine the contribution of recent transmission to spread of drug-resistant tuberculosis in Texas, we performed IS6110-based and pTBN12-based restriction fragment length polymorphism (RFLP) analyses on Mycobacterium tuberculosis isolates. Isolates collected from 201 patients in Texas between 1992 and 1994 were studied. The distribution of cases was strikingly focal. All cases were reported from 35 of the 254 counties in Texas, and 74% (148 of 201) were reported from only 9 counties. One hundred sixty-one (80%) of the patients had M. tuberculosis isolates with unique RFLP patterns, and 41 (20%) patients were in 20 clusters, each comprising 2 to 3 patients. The largest number of cases of drug-resistant tuberculosis were reported in counties bordering Mexico, but the percentage of clustered cases was highest in northeast Texas and in counties that included the cities of Dallas, Fort Worth, and Houston. Compared to nonclustered patients, clustered patients were more likely to be African American and to have been born in the United States. Clustered patients were significantly more likely to be from the same geographic area, and clustered patients from the same geographic area were more likely to have isolates with identical drug susceptibility patterns, suggesting that they were linked by recent transmission. In 11 of 20 clusters, clustered patients were from geographically separate regions, and most isolates did not have identical drug susceptibility patterns, suggesting that tuberculosis was contracted from a common source in the remote past. Based on the low percentage of clustered cases and the small cluster size, we conclude that there is no evidence for the extensive transmission of drug-resistant tuberculosis in Texas.

Adolescent↗

PubMed1998

Characterization of the monovalent and divalent cation requirements for the xenobiotic carboxylic acid: CoA ligases of bovine liver mitochondria.

The XL-I, XL-II and XL-III forms of xenobiotic/medium-chain fatty acid: CoA ligase were found to be inactive toward benzoate in the absence of either monovalent or divalent cations. The absolute requirement for monovalent cation was satisfied by either K+, Rb+, or NH4+. Na+ only supported a very low rate. Varying the nature of the anion had only a minor effect. For XL-I and XI-II, the optimum concentration of K+ was 50 mM; higher (physiologic) concentrations led to a decrease in activity. K+ did not inhibit XL-III. The absolute requirement for divalent cation was satisfied by Mg2+ or Mn2+, or to a lesser extent by Co2+ or Fe2+. For the XL-I and XL-II, excess uncomplexed Mg2+ or Mn2+ decreased the rate; the optimum concentration of Mn2+ was approximately the same as the concentration of ATP in the assay, and the optimum concentration of Mg2+ was approximately double the concentration of ATP in the assay. This is consistent with the concept that the divalent cation is required to complex with ATP and with the known stability constants for the ATP complexes of these two divalent cations. XL-III was not inhibited by uncomplexed divalent cations. Uncomplexed ATP was a moderate inhibitor of XL-I and XL-II, and a weak inhibitor of XL-III. The data indicate that in vivo benzoate conjugation is K+ and Mg2+ dependent, and that the cation effects are complex and differ for XL-I and XL-II as compared with XL-III.

Adenosine Triphosphate↗

PubMed1998

Development of a radiolabeled ATP assay for carboxylic acid:CoA ligases and its use in the characterization of the xenobiotic carboxylic acid:CoA ligases of bovine liver mitochondria.

A radiolabeled ATP assay was developed for measuring carboxylic acid:CoA ligase activity. The assay was designed to measure the formation of [gamma-33P]pyrophosphate from [gamma-33P]ATP in the course of the reaction. The assay was linear with protein concentration, and rates as low as 1 pmol/min were measurable. Rates determined with this assay were in agreement with rates determined with [14C]carboxylic acids. The assay was used to characterize the substrate specificity of the XL-I, XL-II, and XL-III ligases from bovine liver mitochondria. Forty carboxylic acids were tested for activity. The enzymes differed in their substrate specificities with XL-I and XL-II being the most similar and XL-III having the broadest specificity. This study has uncovered 19 new carboxylic acids that are substrates for these enzymes.

Adenosine Triphosphate↗