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Biomedical subjects

M Fukase

Publications and source records attributed to M Fukase.

At least 55 records · Page 3Linked to original sources
PubMed1994

A serine protease in soybean seeds that acts specifically on the native alpha subunit of beta-conglycinin.

A proteolytic activity directed against the alpha subunit of beta-conglycinin was detected in resting mature seeds of the soybean [Glycine max (L.) Merrill] cultivar Keburi. The relationship between pH and activity and the effect of protease inhibitors revealed that the enzyme was a neutral/alkaline serine protease. The proteolysis of the alpha subunit of beta-conglycinin yielded a specific product with a molecular weight of about 47,000, as determined by SDS-PAGE, but the enzyme had no activity against the beta subunit. The amino acid composition, the molecular weight and the amino-terminal amino acid sequence of the proteolytic product revealed that the action of the enzyme on the alpha subunit was specific, with cleavage occurring only at the R126-R127 peptide bond of the alpha subunit. These characteristics of the protease indicate that the enzyme is a novel protease that has not previously been recognized in soybean seeds.

Amino Acid Sequence↗
PubMed1994

Chronic myelomonocytic leukemia following prolonged alkylating agent therapy for multiple myeloma.

A 35-year-old male presented with chronic myelomonocytic leukemia (CMMoL) after 6.5 years of alkylating agent therapy for IgG-kappa type multiple myeloma. The total dose of melphalan was 0.648 g. CMMoL was stable with weekly injection of alpha-interferon for one year. Thereafter, monocytosis and thrombocytopenia aggravated, and the patient died of disseminating intravascular coagulation. Prolonged drug therapy can induce CMMoL, as well as other myelodysplastic syndromes.

Adult↗
PubMed1994

Retinoic acid differentially affects platelet-derived growth factor and epidermal growth factor-regulated cell growth of mouse osteoblast-like cells.

Retinoic acid (RA) plays an important role in the control of cell growth and differentiation. To elucidate the effects of RA for osteoblasts, we examined here the responsiveness of normal osteoblast-like MC3T3-E1 cells treated with RA for two growth factors, platelet-derived growth factor (PDGF) and epidermal growth factor (EGF). The transcripts of alpha- and gamma-RA receptors were constitutively expressed in MC3T3-E1 cells, and the expression of the beta-RA receptor mRNA was induced by RA. The PDGF-induced mitogenicity of MC3T3-E1 cells was significantly enhanced by 1 microM RA pretreatment, whereas the EGF-induced mitogenicity was suppressed by the same treatment. The expression of both alpha- and beta-PDGF receptor gene products detected by RNA blot and immunoblot analyses was significantly increased by RA. The increased expression of PDGF receptors was accompanied by the augmentation of PDGF-induced receptor autophosphorylation following the enhancement of inositol phosphate hydrolysis. In contrast, EGF-induced receptor autophosphorylation was suppressed in RA-treated cells, whereas the expression level of EGF receptor was not affected. These findings demonstrate that RA could control the cell growth of osteoblast-like MC3T3-E1 cells not only by regulating the gene expression of growth factor receptors, but also by modulating the ligand-induced receptor autophosphorylation.

Animals↗
PubMed1993

Involvement of dual signal transduction systems in the stimulation of osteoclast-like cell formation by parathyroid hormone and parathyroid hormone-related peptide.

The present study was performed to examine whether parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP) would stimulate osteoclast-like cell formation via soluble factor(s) released from osteoblasts and, if so, to characterize the involvement of PTH/PTHrP-responsive dual signal transduction systems [cAMP-dependent protein kinase (PKA) and calcium/protein kinase C(PKC)]. Osteoblasts-conditioned medium (CM) was obtained from rat osteoblastic osteosarcoma cells (UMR-106 cells), which had been cultured in serum free medium for 24 hrs after treatment with various kinds of reagents. The CM of osteoblasts treated with either 10(-7) M human(h) PTH-(1-34) or 10(-7)M hPTHrP-(1-34) equally stimulated osteoclast-like cell formation from hemopoietic blast cells derived from mouse spleen cells, although the CM treated with 10(-8) M 1,25dihydroxyvitamin D3 failed to affect it. The CM treated with both 10(-4) M dibutyryl-cAMP and a direct PKA activator, 10(-4)M Sp-cAMPS significantly increased osteoclast-like cell formation. The CM treated with a PKC activator, 10(-7)M phorbol 12-myristate 13-acetate (PMA) and calcium ionophores (10(-7)M A23187 and 10(-7)M ionomycin) also significantly enhanced osteoclast-like cell formation. The present study first indicated that osteoblast-mediated stimulation of osteoclast-like cell formation by PTH and PTHrP, and the participation of PTH/PTHrP-responsive dual signal transduction systems of osteoblasts in the stimulation of osteoclast-like cell formation by PTH and PTHrP.

Animals↗
PubMed1993

Effect of 1,25-dihydroxyvitamin D3 on the proliferation of osteoblastic MC3T3-E1 cells by modulating the release of local regulators from monocytes.

Some evidence suggests an important role of mononuclear cells at the bone remodeling sites in the coupling of bone resorption to bone formation. Therefore, we examined effects of human monocytes-conditioned medium (CM) treated with 1,25-dihydroxyvitamin D3 [1.25(OH)2D3] on the proliferation of osteoblastic MC3T3-E1 cells. 1,25(OH)2D3 (10(-11)-10(-8) directly inhibited [3H]thymidine incorporation (TdR) into MC3T3-E1 cells in a dose-related fashion. 24,25(OH)2D3 and 25(OH)D3 (10(-8) and 10(-7) M) had only modest inhibitory effect, compared to that of 1,25(OH)2D3. CM, per se, on the other hand, significantly stimulated TdR, whereas CM obtained from monocytes treated with 1,25(OH)2D3(10(-10) and 10(-8) M) significantly inhibited TdR. Treatment of monocytes with 10(-7) M 25(OH)D3 significantly inhibited CM-induced stimulation of TdR to a lesser degree, compared to that of 10(-8) M 1,25(OH)2D3 and treatment of monocytes with 10(-7) M 24,25(OH)2D3 did not affect CM-induced stimulation of TdR. The inhibition of TdR by 1,25(OH)2D3-treated CM was significantly blocked by 10(-6) M indomethacin, an inhibitor of prostaglandin synthesis. Present data first indicate that 1,25(OH)2D3 inhibited osteoblast proliferation not only directly but also indirectly through modulating the release of local factors as to bone remodeling from monocytes, and also suggest that its indirect effect via monocytes was mediated at least in part through prostaglandin synthesis.

Bone Resorption↗
PubMed1993

Cross talk of dual-signal transduction systems in the regulation of DNA synthesis by parathyroid hormone in osteoblastic osteosarcoma cells.

There has been recent evidence that calcium/protein kinase C (Ca/PKC) messenger system as well as adenylate cyclase are involved in the signal transduction stimulated by PTH. We therefore examined the role of these dual-signal transduction systems and the interaction of these systems in the regulation of DNA synthesis by PTH in the osteoblastic osteosarcoma cells, UMR-106. As recently reported, 10(-4) M Sp-cAMPS, a direct activator of cAMP-dependent protein kinase (PKA), and 10(-4) M dibutyryl-cAMP, as well as hPTH-(1-34), caused the significant inhibition of [3H]thymidine incorporation (TdR). Both A23187 and ionomycin (10(-8)-10(-6) M) inhibited TdR in a dose-dependent manner, with a minimal effective dose at 10(-7) M. Although 10(-6) M phorbol 12-myristate 13-acetate (PMA) caused slight but significant stimulation of TdR by itself, it augmented not only dibutyryl-cAMP- but also Sp-cAMPS-induced inhibition of TdR. On the other hand, 4 alpha-phorbol 12,13-didecanoate, incapable of activating PKC, failed to augment these cAMP analogs-induced effects. Pretreatment with 50 microM H-7, an inhibitor of PKC, not only abolished the PMA-induced augmentation of effect by cAMP analogs but also significantly blocked the PTH-induced inhibitory effect on TdR. Pretreatment with 10(-6) M PMA, which downregulates PKC, significantly inhibited the PTH-induced suppression of TdR. Combined treatment with cAMP analog (dibutyryl-cAMP or Sp-cAMPS) and calcium ionophore (A23187 or ionomycin) caused additive effects on TdR, and PMA used in combination with both cAMP analog and calcium ionophore induced the further inhibition of TdR.(ABSTRACT TRUNCATED AT 250 WORDS)

Bucladesine↗
PubMed1993

Age- and gender-related changes in body composition in Japanese subjects.

Age-dependent changes in body composition, namely a decrease in bone mass and lean mass and a reciprocal increase in fat mass, are often observed in normal populations. The recent development of dual-energy x-ray absorptiometry (DXA) made it possible to analyze bone mineral content (BMC), fat mass (fat), and lean body mass (LBM) more precisely and easily. We measured BMC, fat, and LBM in Japanese subjects by DXA to describe the changes in body composition with aging in the Japanese population. A total of 34 female (aged 20-74) and 34 male (aged 18-78) volunteers were divided into three groups according to their age: young (18-22 years), middle-aged (39-48 years), and old (61-78 years). Mean values for body height (BH), body weight (BW), and body mass index (BMI) of the subjects were very similar to Japanese normative values. The BMI of the middle-aged group was the highest of all groups of both sexes. BMC decreased significantly with aging in females but not in males. A decrease in LBM and a reciprocal increase in fat were found between young and middle-aged males but not in females. The correlation between BMC and LBM tends to be greater in males than in females. On the other hand, the correlation between BMC and fat was greater in females than males. These results demonstrate the age- and gender-related difference in body components in Japanese subjects. DXA may be useful for the analysis of body composition in different age and sex groups.

Absorptiometry, Photon↗
PubMed1993

Interaction of parathyroid hormone-related peptide-responsive dual signal transduction systems in osteoblastic osteosarcoma cells: role in PTHrP-induced homologous desensitization.

In osteoblastic UMR-106 cells, 10(-7) M human (h) PTH-related peptide (PTHrP)-(1-34) significantly induced the formation of total inositol phosphates to the same degree as 10(-7) M hPTH-(1-34), confirming that in addition to cAMP-dependent protein kinase (PKA), PTHrP possesses another signal transduction system, calcium/protein kinase C (Ca/PKC). Experiments were therefore performed to characterize the cross talk of these dual-signal transduction systems and its participation in the PTHrP-induced homologous desensitization of cAMP and cytosolic calcium (Cai) response in osteoblasts. Preincubation with 10(-7) M hPTHrP-(1-34) caused homologous desensitization, resulting in a remarkable decrease in cAMP accumulation in response to further exposure to PTHrP. This effect was significant after 2 h pretreament and reached a maximum at 6 h. Pretreatment with the PKC-activating phorbol ester phorbol 12-myristate-13-acetate (PMA, 10(-6) M) for 30 minutes and 6 h caused a significant increase and decrease in cAMP responsiveness to PTHrP, respectively. Pretreatment with calcium ionophores (A23187 or ionomycin, 10(-6) M), not for 30 minutes but for 6 h, caused a significant decrease in cAMP responsiveness to PTHrP. H-7 (an inhibitor of PKC, 50 microM) significantly blocked not only PMA- but also PTHrP-induced desensitization of the cAMP response. PTHrP caused the complete homologous desensitization of an increase in Cai within 30 minutes. Pretreatment with dibutyryl-cAMP (10(-4) M) for 30 minutes caused significant inhibition of the PTHrP-induced increase in Cai, and pretreatment with Sp-cAMPS (10(-4) M), a direct activator of PKA, for 30 minutes completely blocked the PTHrP-induced increase in Cai.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1993

Effects of high calcium concentration on the functions and interactions of osteoblastic cells and monocytes and on the formation of osteoclast-like cells.

The present study was performed to clarify the role of high calcium concentration and the appearance of mononuclear cells at the resorptive site in bone remodeling. Our recent study revealed that the high concentration of extracellular calcium ([Ca2+]e) stimulated DNA synthesis in osteoblastic MC3T3-E1 cells not only directly but also indirectly via monocytes. Human monocyte-conditioned medium (CM) significantly stimulated DNA synthesis and inhibited alkaline phosphatase (ALP) activity. In contrast, when monocytes were cultured at high [Ca2+]e concentrations (more than 3 mM), CM from these monocytes significantly stimulated ALP activity in MC3T3-E1 cells. Such stimulatory effect of CM was not observed at a high magnesium concentration (Mg2+, 5 mM). Treatment of monocytes with the calcium ionophore A23187 did not affect the CM-induced effect on DNA synthesis and ALP activity in these cells. To determine the migration potency of MC3T3-E1 cells and monocytes toward the high [Ca2+]e, chemotaxis assay was performed. The increasing [Ca2+]e (more than 3 mM) induced a chemotactic response of MC3T3-E1 cells as well as monocytes, but the high concentration of Mg2+ (5 mM) did not induce it. On the other hand, treatment with high [Ca2+]e (more than 3 mM) or CM significantly inhibited the 1,25-(OH)2D3-induced formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNC) from their precursors derived from mouse spleen cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1993

Calcium supplementation in osteoporosis.

Although calcium is the most abundant inorganic constituent of the bone, indispensable for the maintenance of its physical strength, the role of calcium nutrition in the development of osteoporosis and the preventive and therapeutic significance of calcium supplementation in osteoporosis have been matters of intense controversy. The wide difference in the baseline nutritional intake of calcium among different groups and the variation in age of the patients studied may have been contributory factors. Emphasis has so far been placed on the rapid bone loss in the immediate postmenopausal period predominantly influenced by estrogen deficiency which has overshadowed the effect of calcium. The strong dependence of the effect of calcium preparation used tends to be forgotten. In the present study employing oyster shell electrolysate as the calcium source in patients with a mean age of approximately 80 years, bone mineral density was kept significantly higher than in age-matched, non-supplemented patients over a period of 2 years. In separate experimental studies, rats maintained on 2% calcium showed higher bone mineral content and lived longer than did controls maintained on 1% calcium. Age-associated deterioration of renal function and hyperlipidemia were also prevented by calcium supplementation.

Aged↗
PubMed1993

Role of dual signal transduction systems in the stimulation of bone resorption by parathyroid hormone-related peptide. The direct involvement of cAMP-dependent protein kinase.

The present study was performed to compare the effect of parathyroid hormone-related peptide (PTHrP) on bone resorption with that of parathyroid hormone (PTH) and clarify the participation of PTHrP-responsive dual signal transduction systems involving cAMP-dependent protein kinase (PKA) and calcium/protein kinase C (Ca/PKC) in the stimulation of bone resorption by PTHrP. Bone resorbing activity was estimated as the number of pits formed on the dentine slice and total area of pits per slice in bone cells derived from 2 week-old mice. Human (h)PTHrP-(1-34) (10(7) M) stimulated bone resorption as potent as hPTH-(1-34) (10(7) M) did. The stimulation of bone resorption by hPTHrP-(1-34) and hPTH-(1-34) was equally blocked by either simultaneous treatment with 10(-8) M Elcatonin (eel calcitonin derivative; from Asahi Chemical Industry, Tokyo, Japan) [corrected] or pretreatment with 10(-7) M [Nle8,18Tyr34]hPTH-(3-34)amide. Rp-cAMPs, an antagonist in the activation of PKA, equally attenuated bone resorption stimulated by PTHrP as well as by PTH. A23187 (10(-7) M) caused a significant stimulation of bone resorption. These findings indicate the direct involvement of PKA activation and a contributory role of an increase in cytosolic calcium in the stimulation of bone resorption by PTHrP and suggest that PTHrP stimulates bone resorption presumably through the same mechanism as PTH does.

Animals↗
PubMed1993

Role of calcium/protein kinase C in the regulation of DNA synthesis by parathyroid hormone-related peptide in osteoblastic osteosarcoma cells.

Our recent study demonstrated the direct involvement of cAMP-dependent protein kinase (PKA) in the regulation of DNA synthesis by PTH-related peptide (PTHrP) in osteoblastic osteosarcoma cells, UMR-106. Since PTHrP has been reported to possess dual signal transduction systems [PKA and calcium/protein kinase C (Ca/PKC]), present study was performed to characterize the involvement of Ca/PKC signal transduction system in the regulation of DNA synthesis by PTHrP in these cells. Human PTHrP-(1-34) (10(-7) M) caused a rapid increase in intracellular Ca ([Ca2+]i), followed by return to the basal level within 1 min. Pretreatment with 10(-4) M TMB-8 or 10(-5) M dantrolene, inhibitors of calcium release from intracellular calcium store, significantly blocked the PTHrP-induced increase in [Ca2+]i, but did not affect the PTHrP-induced inhibition of DNA synthesis. Pretreatment with 50 uM H-7 or 1 nM staurosporine, inhibitors of PKC, significantly blocked the PTHrP (10(-9) to 10(-7) M)-induced inhibition of DNA synthesis. Pretreatment with 10(-6) M phorbol 12-myristate 13-acetate, which downregulated PKC, significantly blocked the inhibition of DNA synthesis by PTHrP. Present study indicates that in addition to PKA activation, PKC activation is coupled to the regulation of DNA synthesis by PTHrP in osteoblasts.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

A membrane-bound metallo-endopeptidase from rat kidney: its immunological characterization.

The structure and location of a membrane-bound metallo-endopeptidase, previously purified from rat kidney [Yamaguchi et al. (1991) Eur. J. Biochem. 200, 563-571], were examined by immunochemical and immunohistochemical methods with a rabbit polyclonal antibody against the purified enzyme. On treatment with endoglycosidase F, the subunit of the purified enzyme (molecular mass = 88 kDa) was converted to a smaller form (78.5 kDa), indicating that the enzyme contained at least 11% N-linked carbohydrate. Treatment of kidney membranes with papain resulted in release of the enzyme, as shown by Western blotting analysis of the solubilized fraction. Immunoassays of rat tissues showed that only the kidney, and small and large intestine expressed significant amounts of the antigen. Moreover, immunohistochemical studies showed that the antigen was confined to the luminal surfaces of the proximal renal tubules and the intestinal villi. Thus, like another kidney membrane metallo-endopeptidase, meprin [Kounnas et al. (1991) J. Biol. Chem. 266, 17350-17357], the purified enzyme is shown to be a glycoprotein that is probably anchored in the plasma membrane, and located in the luminal surface of microvillar membranes of the kidney and intestine. These results indicate that our enzyme and meprin have clear structural and topological similarities.

Animals↗
PubMed1993

alpha-Fetoprotein producing gastric carcinomas: a comparative study of three different subtypes.

Nine cases of gastric carcinoma with excessive production of alpha-fetoprotein (AFP) were analyzed morphologically, histochemically and biochemically. Consequently, it was proposed that AFP-producing gastric carcinomas should be divided into three subtypes: (i) hepatoid type; (ii) yolk sac tumor-like type; and (iii) fetal gastrointestinal type. The data from the study suggested that the hepatoid type and the yolk sac tumor-like type are derived from liver cell metaplasia and yolk sac cell metaplasia of common poorly differentiated medullary adenocarcinoma, respectively. The fetal gastrointestinal type seemed to be a result of the imitation of fetal gastrointestinal epithelium by common tubular adenocarcinoma. The hepatoid type was also the most common in the file of AFP-producing gastric carcinoma. Unfortunately, most of the hepatoid types seemed to be highly malignant.

Aged↗
PubMed1993

Second messenger signaling of PTH- and PTHRP-stimulated osteoclast-like cell formation from hemopoietic blast cells.

The second messenger signaling mechanisms of parathyroid hormone (PTH)- and PTH-related peptide (PTHRP)-stimulated osteoclast-like cell formation were investigated in mouse hemopoietic blast cells that possessed PTH binding sites. Human (h) PTH-(1-34) or hPTHRP-(1-34) resulted in a dose-dependent stimulation of tartrate-resistant acid phosphatase-positive multinucleated cells (MNC) formation. Pretreatment with [Nle8,18Tyr34]hPTH-(3-34) significantly blocked hPTH-(1-34)- and hPTHRP-(1-34)-stimulated MNC formation. Dibutyryladenosine 3',5'-cyclic monophosphate (10(-4) M) and forskolin (10(-5) M) as well as the stimulatory diastereoisomer of adenosine 3',5'-cyclic phosphorothioate (Sp-cAMPS), a direct activator of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (PKA) (10(-4) M), stimulated MNC formation, and Rp-cAMPS, an inhibitor of PKA activation (10(-4) M), almost completely inhibited MNC formation stimulated by the aforementioned agents but not by 1,25-dihydroxyvitamin D3. Moreover, Rp-cAMPS significantly blocked PTH- and PTHRP-stimulated MNC formation. Treatment with calcium ionophores (10(-8) and 10(-7) M) and phorbol 12-myristate 13-acetate, a protein kinase C (PKC) activator (10(-8) to 10(-6) M), but not 4 alpha-phorbol 12,13-didecanoate, a phorbol incapable of activating PKC, stimulated MNC formation. Two PKC inhibitors [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine dihydrochloride and staurosporine] equally blocked PTH- and PTHRP-stimulated MNC formation. The combined pretreatment with Rp-cAMPS and PKC inhibitors completely blocked PTH- and PTHRP-stimulated MNC formation. Present findings indicate that the activation of PKA and PKC is directly linked to PTH- and PTHRP-stimulated osteoclast-like cell formation from hemopoietic blast cells.

Animals↗
PubMed1993

Individual and combined effects of intact PTH, amino-terminal, and a series of truncated carboxyl-terminal PTH fragments on alkaline phosphatase activity in dexamethasone-treated rat osteoblastic osteosarcoma cells, ROS 17/2.8.

The individual and combined effects of intact PTH, amino-terminal, and a series of truncated carboxyl-terminal PTH fragments on alkaline phosphatase activity were examined in dexamethasone-treated rat osteoblastic osteosarcoma cells ROS 17/2.8. Dexamethasone-induced alkaline phosphatase activity was inhibited not only by hPTH(1-84) and amino-terminal PTH fragment hPTH(1-34), but also by carboxyl-terminal PTH fragment hPTH(69-84) in a dose-related fashion. At 10(-7) mol/l, hPTH(1-84) completely abolished dexamethasone-induced alkaline phosphatase activity, while hPTH(1-34) and hPTH(69-84) reduced alkaline phosphatase activity to 0.16 +/- 0.02 and 0.80 +/- 0.03 fold, respectively, of the control value obtained in the absence of PTH peptides. The combination of hPTH(1-34) and hPTH(69-84) resulted in reduction of alkaline phosphatase activity to the level obtained by hPTH(1-84). The shorter carboxyl-terminal PTH fragment hPTH(71-84) did not affect alkaline phosphatase activity or modulate the action of hPTH(1-34). The longer carboxyl-terminal PTH fragment hPTH(53-84) stimulated alkaline phosphatase activity up to 1.23 +/- 0.03 fold and partially blunted the inhibitory effect of hPTH(1-34) on alkaline phosphatase activity. These findings suggest that carboxyl-terminal PTH fragments could exert diverse effects on the target cells, depending on the length of deletion of amino-terminal amino acids of PTH molecule, and interact with amino-terminal PTH fragment. The two amino-terminal amino acids of hPTH(69-84) and the 53-68 portion of hPTH(53-84) might be responsible for the respective inhibitory and stimulatory effects of the peptides on alkaline phosphatase activity.

Alkaline Phosphatase↗
PubMed1992

Endothelin 1 hydrolysis by rat kidney membranes.

Hydrolysis of endothelin 1 by rat kidney membranes was investigated using a reverse-phase HPLC and an automated gas-phase protein sequencer. Endothelin 1 was hydrolyzed into four major fragments which were detected by HPLC. Phosphoramidon, an inhibitor of neutral endopeptidase 24,11, almost completely suppressed the production of three fragments, but one fragment was not affected by the inhibitor. Analysis of N-terminal sequences of the degradation products revealed that the phosphoramidon-sensitive fragments were generated by cleavage at the Ser5-Leu6 bond of endothelin 1 that was identical with its cleavage site by purified rat endopeptidase 24,11, reported previously. The phosphoramidon-insensitive fragment was produced by cleavage at Leu17-Asp18, which was distinct from the sites by endopeptidase 24,11, but corresponded to that by a phosphoramidon-insensitive metallo-endopeptidase recently isolated from rat kidney membranes by us [(1992) Eur. J. Biochem. 204, 547-552]. Kinetic determination of endothelin 1 hydrolysis by the isolated enzyme yielded values of Km = 71.5 microM and kcat = 1.49 s-1, giving a ratio of kcat/Km = 2.08 x 10(4) s-1.M-1. The Km value was much higher and the kcat/Km value was much lower than those for rat endopeptidase 24,11 reported previously. Thus, endopeptidase 24,11 appears to hydrolyze endothelin 1 more efficiently than the isolated enzyme does. Both enzymes may play physiological roles in the metabolism of endothelin 1 by rat kidney membranes in vivo.

Amino Acid Sequence↗