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PubMed1978

Dimeric nature and amino acid compositions of homogeneous canine prostatic human liver and rat liver acid phosphatase isoenzymes. Specificity and pH-dependence of the canine enzyme.

Two isoenzymes of rat liver acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum) EC 3.1.3.2) have been purified to homogeneity, at least one of these for the first time. Both of the rat liver isoenzymes have identical specific activities towards p-nitrophenyl phosphate. Molecular weights of the native enzymes are 92 000 for rat liver isoenzyme I and 93 000 for isoenzyme II, while the subunit molecular weights are 51 000 and 52 000 respectively. Data on substrate specificity and pH dependence are presented for the homogeneous canine prostatic enzyme, which is also isolated as a dimeric enzyme of (native) molecular weight 89 000. Carbohydrate analysis data are presented for canine prostatic acid phosphatase and it is further noted that both isoenzymes of rat liver acid phosphatase are also glycoproteins. The amino acid compositions of the two rat liver isoenzymes are presented together with those of the similar dimeric acid phosphatase of human liver and of canine prostate. Comparison of these results with published data for the amino acid composition of human prostatic acid phosphatase shows substantial similarities. However, significant differences are seen in the amino acid composition of rat liver acid phosphatase isoenzyme I as compared to a previous literature report. Most notably, 17 histidine residues are found per mol of isoenzyme I and 18 for isoenzyme II.

Acid Phosphatase↗
PubMed1984

Distribution and characterization of cAMP-dependent protein kinase isoenzymes in bovine adrenal cells.

Subcellular localization and characterization of cAMP-kinase isoenzymes in fasciculata reticularis bovine adrenal cells has been investigated. Different subcellular fractions were purified on a Percoll gradient and characterized by marker enzymes. cAMP-kinase was located principally in cytosol and microsomes. In the low-speed particulate fractions cAMP-kinase was found associated mainly with plasma membrane but not with mitochondria. Characterization of isoenzyme patterns in subcellular fractions by conventional DEAE-cellulose chromatography and by anion-exchange HPLC gives essentially the same results. Isoenzyme I appears to be the main enzyme in cytosol whereas isoenzyme II predominates in solubilized microsome and plasma membrane enriched fraction. Photoaffinity labelling of chromatographic fractions demonstrated that HPLC separates both cAMP binding subunits. Photoaffinity labelling of the different subcellular fraction by 8-azido-[32P]cAMP confirmed the data obtained by anion-exchange chromatography. However, in microsomes this method revealed the presence of both isoenzymes and the preferential solubilization of isoenzyme II by Triton X-100. In summary, our results indicate a subcellular compartmentalization of cAMP-kinase in bovine adrenal cells with a preferential localization of isoenzyme I in cytosol and of isoenzyme II in membrane. However, the relation between the distribution and the role of each isoenzyme has so far not been documented.

Adrenal Glands↗
PubMed1992

Modular mutagenesis of exons 1, 2, and 8 of a glutathione S-transferase from the mu class. Mechanistic and structural consequences for chimeras of isoenzyme 3-3.

Exons 1 and 2 and exon 8 of the mu class GSH transferases from rat encode sequence-variable regions 1 and 4 of mu class isoenzymes, respectively. These two of four variable regions are located at the N- and C-termini of this isoenzyme class and impinge on the active site. In order to assess the influence of these variable regions on the catalytic diversity of the class mu isoenzymes, seven chimeric isoenzymes were constructed by transplantation of the variable regions of the sequence of the type 4 subunit into the corresponding regions of the type 3 subunit. The chimeric isoenzymes exhibit unique catalytic properties. Replacement of all, or part, of variable region 4 of the type 3 subunit with that of the type 4 subunit results in chimeric catalysts with higher turnover numbers in nucleophilic aromatic substitution reactions. Analysis of the crystal structure of isoenzyme 3-3 [Ji, X., Zhang, P., Armstrong, R. N., & Gilliland, G. L. (1992) Biochemistry (preceding paper in this issue)] suggests that interaction of the flexible C-terminal tail with the N-terminal domain helps limit the rate of product release from the active site of isoenzyme 3-3 in this type of reaction. Substitution of all, or part, of the sequence-variable region 1 of subunit 3 with that of subunit 4 results in chimeric isoenzymes that mimic the high stereoselectivity but not the catalytic efficiency of isoenzyme 4-4 toward alpha,beta-unsaturated ketones.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1983

Kinetic properties of human liver alcohol dehydrogenase: oxidation of alcohols by class I isoenzymes.

Class I isoenzymes of alcohol dehydrogenase (ADH) were isolated by chromatography of human liver homogenates on DEAE-cellulose, 4-[3-[N-(6-aminocaproyl)-amino]propyl]pyrazole--Sepharose and CM-cellulose. Eight isoenzymes of different subunit composition (alpha gamma 2, gamma 2 gamma 2, alpha gamma 1, alpha beta 1, beta 1 gamma 2, gamma 1 gamma 1, beta 1 gamma 1, and beta 1 beta 1) were purified, and their activities were measured at pH 10.0 by using ethanol, ethylene glycol, methanol, benzyl alcohol, octanol, cyclohexanol, and 16-hydroxyhexadecanoic acid as substrates. Values of Km and kcat for all the isoenzymes, except beta 1 beta 1-ADH, were similar for the oxidation of ethanol but varied markedly for other alcohols. The kcat values for beta 1 beta 1-ADH were invariant (approximately 10 min-1) and much lower (5-15-fold) than those for any other class I isoenzyme studied. Km values for methanol and ethylene glycol were from 5- to 100-fold greater than those for ethanol, depending on the isoenzyme, while those for benzyl alcohol, octanol, and 16-hydroxyhexadecanoic acid were usually 100-1000-fold lower than those for ethanol. The homodimer beta 1 beta 1 had the lowest kcat/Km value for all alcohols studied except methanol and ethylene glycol; kcat values were relatively constant for all isoenzymes acting on all alcohols, and, hence, specificity was manifested principally in the value of Km. Values of Km and kcat/Km revealed for all enzymes examined that the short chain alcohols are the poorest while alcohols with bulky substituents are much better substrates. The experimental values of the kinetic parameters for heterodimers deviate from the calculated average of those of their parent homodimers and, hence, cannot be predicted from the behavior of the latter. Thus, the specificities of both the hetero- and homodimeric isoenzymes of ADH toward a given substrate are characteristics of each. Ethanol proved to be one of the "poorest" substrates examined for all class I isoenzymes which are the predominant forms of the human enzyme. On the basis of kinetic criteria, none of the isoenzymes of class I studied oxidized ethanol in a manner that would indicate an enzymatic preference for that alcohol.

Alcohol Dehydrogenase↗
PubMedDate not supplied

Carboxylesterase isoenzyme specific deacylation of diacetoxyscirpenol (anguidine).

The deacylation reaction of diacetoxyscirpenol (DAS), a trichothecene mycotoxin, was studied by using five carboxylesterase isoenzymes isolated from mouse liver microsomes. The simultaneous isolation of the five microsomal carboxylesterase isoenzymes was accomplished by chromatofocusing. DAS serves as a unique substrate since both acetyl groups are accessible for hydrolysis, providing an opportunity to investigate the regioselective hydrolysis of DAS with the various isoenzymes. A novel basic carboxylesterase isoenzyme, pI 8.4-8.2, was isolated. This isoenzyme exhibits strict regioselectivity toward DAS hydrolysis; only the acetyl group at C-4, but not that at C-15, is hydrolyzed. Moreover, this is the major isoenzyme responsible for the deacylation of DAS in mouse hepatic microsomes. The rate constant determined for deacylation of DAS at C-4 for this isoenzyme is 130-1000 times greater than that of the other carboxylesterases. This isoenzyme was also the most efficient for the hydrolysis of 4-monoacetoxyscirpenediol with a rate constant 30-100 times greater than that of the other isoenzymes.

Animals↗
PubMed1996

Glutathione-S-transferase activity and isoenzyme levels measured by two methods in ovarian cancer, and their value as markers of disease outcome.

A study has been carried out to investigate the cellular distribution and levels of glutathione-S-transferase isoenzymes (GST), acidic (pi), basic (alpha) and neutral (mu), in ovarian tumour biopsies, and to measure GST activity in the same tumour specimens. Two methods of assessing isoenzyme levels (immunohistochemistry and Western blot) were compared. Well-known important clinicopathological features were correlated with response to treatment, overall survival and progression-free survival for each of 97 patients from whom biopsies had been obtained. The glutathione-S-transferase isoenzyme levels were also correlated with overall and progression-free survival, and with the important clinicopathological features. As expected, there was a significant correlation between FIGO stage, histological grade of tumour, amount of residual disease after staging laparotomy, response to chemotherapy, and both overall and progression-free survival. Glutathione-S-transferase isoenzyme levels (acidic, basic and neutral) measured by Western blot were not found to be significantly correlated with any of the clinicopathological parameters tested. Using the immunohistochemistry method of detection there was a correlation between the GST acidic isoenzyme level and the amount of residual disease remaining after initial debulking surgery (higher levels were detected in the group with no residual disease, P=0.034), and also between the GST acidic isoenzyme level and the type of chemotherapy regimen used. Higher levels of the acidic isoenzyme were present in tumour biopsies taken from the patient group who had received a combination regimen (cyclophosphamide, carboplatin, ifosfamide and doxorubicin). The neutral and basic GST isoenzyme levels were not significantly correlated with any of the clinicopathological parameters. None of the GST isoenzyme levels were significantly correlated with response to treatment, overall survival or progression-free survival (using either method of detection). Similarly, glutathione transferase activity showed no significant correlation with prognosis or survival.

Adult↗
PubMed1976

Organ distribution of rat histidine-pyruvate aminotransferase isoenzymes.

The organ distribution of rat histidine-pyruvate aminotransferase isoenzymes 1 and 2 was examined by using an isoelectric-focusing technique. Isoenzyme 1 (pI8.0) is present only in the liver and its activity is increased by the injection of glucagon, whereas isoenzyme 2 (pI5.2) is distributed in all tissues (liver, kidney, brain and heart) tested, and is not affected by glucagon injection. Isoenzyme 2 of the liver, kidney, brain and heart was purified by the same procedure and characterized. Isoenzyme 2 preparations from these four tissues were nearly identical in physical and enzymic properties. These properties differed from those previously found for the highly purified isoenzyme 1 preparation of rat liver. Isoenzyme 2 was active with pyruvate but not with 2-oxoglutarate as amino acceptor. Amino donors were effective in the following order of activity: tyrosine greater than histidine greater than phenylalanine greater than kynurenine greater than tryptophan. Very little activity was found with 5-hydroxytryptophan. The apparent Km for histidine was about 0.45 mM. The Km for pyruvate was about 4.5 mM with histidine as amino donor. The amino-transferase activities of isoenzyme 2 towards phenylalanine and tyrosine were inhibited by histidine. The ratio of aminotransferase activities towards these three amino acids was constant through gel filtration, electrophoresis, isoelectric focusing and sucrose-density-gradient centrifugation of the purified isoenzyme 2 preparations. These results suggest that these three activities are properties of the same enzyme protein. Sephadex G-150 gel filtration and sucrose-density-gradient centrifugation yielded mol.wts. of approx. 95000 and 92000 respectively. The pH optimum was between 9.0 and 9.3.

Animals↗
PubMed1984

Characteristics of selective activation of cyclic AMP-dependent protein kinase isoenzymes by calcitonin and prostaglandin E2 in human breast cancer cells.

The characteristics of the cyclic AMP-dependent protein kinase isoenzyme response to calcitonin stimulation have been studied in two human breast cancer cell lines, T47D and MCF 7. Both cell lines possess calcitonin receptors, a calcitonin-responsive adenylate cyclase and the two isoenzymes of the cyclic AMP-dependent protein kinase, types I and II. The adenylate cyclase also responds to prostaglandin E2. Acute activation of the cyclic AMP-dependent protein kinase isoenzymes was determined by using a modification of a multiple small anion exchange column method [Livesey, Kemp, Re, Partridge & Martin (1982) J. Biol. Chem. 257, 14983-14987]. Control experiments showed that post-extraction activation did not influence the data. Calcitonin caused a rapid, selective activation of isoenzyme II in the T 47D cells with half-maximal response at 10(-10)M, and persisting for at least 24h. In MCF 7 cells calcitonin also caused a highly selective activation of isoenzyme II with half-maximal response at 5 X 10(-11) M, but the response was transient with a return to basal isoenzyme activity by 4-6 h. At this time further addition of calcitonin did not restimulate the cyclic AMP-dependent kinase activity. In neither cell line did calcitonin treatment result in activation of isoenzyme I. Prostaglandin E2, on the other hand, the only significant alternative agonist of adenylate cyclase in T 47D cells, activated isoenzymes I and II to an equal extent in these cells, illustrating that two hormones activating adenylate cyclase in the one cell type might exert different effects by their selective actions upon protein kinase isoenzymes.

Breast Neoplasms↗
PubMed1994

Characterization of calmodulin-dependent cyclic nucleotide phosphodiesterase isoenzymes.

Calmodulin-dependent phosphodiesterase (CaMPDE) is one of the key enzymes involved in the complex interactions which occur between the cyclic-nucleotide and Ca2+ second-messenger systems. Calmodulin-dependent phosphodiesterase exists in different isoenzymic forms, which exhibit distinct molecular and/or catalytic properties. The kinetic properties suggest that the 63 kDa brain isoenzyme is distinct from the brain 60 kDa and heart and lung CaMPDE isoenzymes. The CaMPDE isoenzymes of 60 kDa from brain, heart and lung are regulated by calmodulin, but the affinities for calmodulin are different. At identical concentrations of calmodulin, the bovine heart CaMPDE isoenzyme is stimulated at a much lower Ca2+ concentration than the bovine brain or lung isoenzymes. The bovine lung CaMPDE isoenzyme contains calmodulin as a tightly bound subunit, so that a change in calmodulin concentration had no effect on the [Ca2+]-dependence of activation of this isoenzyme. These observations are consistent with the notion that differential regulation by calmodulin and Ca2+ is an important function of these isoenzymes, which provide fine-tuning mechanisms for calmodulin action.

Animals↗
PubMed1976

[The diagnostic value of CK-isoenzymes in suspected acute myocardial infarction (author's transl)].

CK-isoenzymes were measured in 31 patients hospitalised for suspected myocardial infarctions who had an increase in serum creatine kinase (CK) above 50 U/l. Of 26 patients with definite evidence of myocardial infarction, MB-isoenzyme--specific for myocardial necrosis--was demonstrated in 24. MB-isoenzyme was no longer detectable in two patients hospitalised 48 hours after the onset of symptoms. In the remaining five patients only MM-isoenzyme was found, the elevated CK activity in three patients having been due to an intramuscular injection, and in two others due to pulmonary embolism. Measurement of CK isoenzymes proved of great diagnostic value in three patients with sudden circulatory arrest of, at first, unknown cause after successful resuscitation. Acute myocardial infarction was proven by the presence of MB-isoenzyme. In one of these patients an additional BB-isoenzyme was seen, possibly due to concomitant cerebral ischaemia. In all other patients (with angina, after cardioversion, or after major surgical operations) only MM-isoenzyme was detected. MB-CK-isoenzyme was found to be a highly specific, as well as sensitive, indicator of myocardial necrosis. This being a rather difficult method, its use is not justified in the routine diagnosis, but in doubtful instances its value can hardly be overestimated.

Adult↗
PubMed1983

Clinical assessment of the electrophoretic separation of alkaline phosphatase isoenzymes.

Over a five-month period, using data from patients in whom alkaline phosphatase (ALP) isoenzyme studies were requested routinely, we compared actual clinical diagnoses with the predicted diagnoses based on the results of electrophoretic separation of ALP isoenzymes on cellulose acetate before and after heat treatment and on elevated enzymatic activity of gamma glutamyl transferase (GGT) and alanine aminotransferase (ALT) activity. ALP isoenzymes were interpreted on a qualitative basis (presence or absence of liver, bone, or other isoenzyme) by individual clinical pathologists. Overall, the consistency of agreement in 61 patients was 66% for GGT, 51% for ALP isoenzymes, and 21% for ALT. In 44 patients with definite diagnoses, the sensitivity and specificity, respectively, of each laboratory test for patients with liver disease were 88 +/- 5.7% and 64 +/- 14.5% (ALP isoenzymes); 88 +/- 5.7% and 91 +/- 8.6% (GGT); and 6 +/- 4.1% and 91 +/- 8.6% (ALT). In patients with bone disease, the sensitivity and specificity of ALP isoenzymes was 75 +/- 10.8% and 86 +/- 6.6%, respectively. The results indicate that isoenzymes as currently performed need to be improved through standardization of the interpretation of ALP isoenzyme patterns to establish uniformity of comments.

Alanine Transaminase↗
PubMed1985

Analysis of isoenzymes in normal and carcinogen-treated human endometrial stromal cells in culture.

The isoenzyme patterns of lactate dehydrogenase (LDH), hexokinase, phosphofructokinase, and aldolase were investigated in cultured normal and carcinogen-treated human endometrial stromal cells. Both normal and carcinogen-treated cells had similar phosphofructokinase and aldolase isoenzymes. Distinctive changes in hexokinase and LDH isoenzyme patterns were found in the carcinogen-treated stromal cells. The LDH isoenzyme patterns of the carcinogen-treated stromal cells were shifted toward the muscle LDH forms. This is comparable to the alteration of LDH isoenzyme profiles observed in cell lines established from human uterine sarcomas. The two tissue culture media used affected the LDH isoenzyme patterns of endometrial stromal cells but differences between the LDH isoenzyme patterns of control and carcinogen-treated cells were detected regardless of the growth medium used. Total LDH activity was not significantly different in control and carcinogen-treated stromal cells. The hexokinase isoenzyme patterns expressed by the carcinogen-treated stromal cells were distinctly different from the normal hexokinase patterns. The treated stromal cells contained both hexokinase I and II, whereas the normal cells contained only hexokinase I. Hexokinase and LDH isoenzyme patterns may serve as markers with which to evaluate carcinogen-induced neoplastic changes in cultured endometrial stromal cells.

Cell Line↗
PubMed1990

Distribution of aspartate aminotransferase activity in yeasts, and purification and characterization of mitochondrial and cytosolic isoenzymes from Rhodotorula minuta [corrected].

The distribution of aspartate aminotransferase activity in yeasts was determined. The number of species of the enzyme in each yeast was determined by zymogram analysis. All the yeasts, except for the genus Saccharomyces, showed two or three activity bands on a zymogram. From among the strains, Rhodotorula minuta [corrected] and Torulopsis candida were selected for examination of the existence of yeast mitochondrial isoenzymes, because these strains showed two clear activity bands on the zymogram and contained a high amount of the enzyme. Only one aspartate aminotransferase was purified from T. candida: the component in the minor band on the zymogram was not an isoenzyme of aspartate aminotransferase. On the other hand, two aspartate aminotransferases were purified to homogeneity from R. minuta [corrected]. The components in the main and minor activity bands on the zymogram were identified as the mitochondrial and cytosolic isoenzymes, respectively, in a cell-fractionation experiment. The enzymatic properties of these isoenzymes were determined. The yeast mitochondrial isoenzyme resembled the animal mitochondrial isoenzymes in molecular weight (subunits and native form), absorption spectrum, and substrate specificity. The amino acid composition was closely similar to that of pig mitochondrial isoenzyme. Rabbit antibody against the yeast mitochondrial isoenzyme, however, did not form a precipitin band with the pig mitochondrial isoenzyme.

Amino Acids↗
PubMed1984

Comparative studies on kinetic behavior of horseradish peroxidase isoenzymes.

Kinetic parameters for each reaction step of the peroxidase-catalyzed reaction were determined by the stopped-flow technique on three distinct isoenzymes: acidic A2, neutral C1, and basic E5. The pH dependence of the reaction for the formation of compound I with hydrogen peroxide was examined. The three isoenzymes had a common ionizing group at about pK 4 which affects the rate constant for the formation of compound I. The heat of ionization determined from the temperature dependence of the dissociation constant of the group strongly suggested that it is of carboxyl nature. The rate constant for isoenzyme A2 was a tenth of those for the other two isoenzymes over the whole range of pH. Furthermore, the thermodynamic parameters of isoenzyme A2 were found to be different from those for the other two isoenzymes. These difference as well as the different behavior in alkaline transition of the isoenzymes are discussed in relation to the sixth ligand of the heme. The rate constant of the reduction of compound I and compound II by ferrocyanide were also determined. In both reduction steps, the pH profiles of the apparent rate constant for isoenzyme A2 and E5 were similar, but they were different from that of C1. The ionization with pK 5.29, which was detected only in isoenzyme C1, may be attributed to a group near the porphyrin ring as a stabilizer for the pi-cation radical.

Chemical Phenomena↗
PubMed2006

Tobacco isoenzyme 1 of NAD(H)-dependent glutamate dehydrogenase catabolizes glutamate in vivo.

Glutamate (Glu) dehydrogenase (GDH, EC 1.4.1.2-1.4.1.4) catalyzes in vitro the reversible amination of 2-oxoglutarate to Glu. The in vivo direction(s) of the GDH reaction in higher plants and hence the role(s) of this enzyme is unclear, a situation confounded by the existence of isoenzymes comprised totally of either GDH beta- (isoenzyme 1) or alpha- (isoenzyme 7) subunits, as well as another five alpha-beta isoenzyme permutations. To clarify the in vivo direction of the reaction catalyzed by GDH isoenzyme 1, [(15)N]Glu was supplied to roots of two independent transgenic tobacco (Nicotiana tabacum) lines with increased isoenzyme 1 levels (S4-H and S49-H). The [(15)N]ammonium (NH(4)(+)) accumulation rate in these lines was elevated approximately 65% compared with a null segregant control line, indicating that isoenzyme 1 catabolizes Glu in roots. Leaf glutamine synthetase (GS) was inhibited with a GS-specific herbicide to quantify any contribution by GDH toward photorespiratory NH(4)(+) reassimilation. Transgenic line S49-H did not show enhanced resistance to the herbicide, indicating that the large pool of isoenzyme 1 in S49-H leaves was unable to compensate for GS and suggesting that isoenzyme 1 does not assimilate NH(4)(+) in vivo.

Glutamate Dehydrogenase (NADP+)↗
PubMed1986

Isoenzyme changes during rat facial development.

A method is presented by which rat facial processes from different stages were obtained in pure fraction. The morphology, and protein and DNA contents in free dissected facial processes were determined. Facial processes of embryonic rats aged 9-15 days were analyzed by isoelectric focusing for their isoenzymic distribution of four enzymes: lactate dehydrogenase, creatine phosphokinase, fructose diphosphate aldolase and phosphoglycerate mutase. A dominance of LDH-5, LDH-4 and LDH-3 isoenzymes was observed. As a comparison, LDH isoenzymes from mandibular and maxillary processes of rat embryos aged 9-11 days only revealed LDH-5 and to a smaller extent LDH-4. The results support the presence of a prominent anaerobic metabolism in these tissues during early facial development. The change to LDH-3 development correlates well with the formation of new blood vessels. From the ninth embryonic day, isoenzyme BB of creatine phosphokinase was present and during days 10-15 MB and MM developed. Isoenzyme A4 of fructose diphosphate aldolase was present from the ninth embryonic day and isoenzymes A3C and A2C2 developed during days 10-15. From the tenth embryonic day, isoenzyme BB of phosphoglycerate mutase was present and during days 10-15 isoenzyme MB and MM developed. Isoenzyme development was first seen in mandibular processes, followed by maxillary, lateral nasal and medial nasal processes, and it preceded morphologic evidence of skeletal muscle formation.

Animals↗
PubMed1968

Comparative regulation of isoenzymic 3-deoxy-D-arabino-heptulosonate 7-phosphate synthetases in microorganisms.

The independent control of regulatory isoenzymes by different metabolites constitutes one well-known pattern of control in branched metabolic pathways. This pattern was previously found to be widely distributed in the aromatic amino acid pathway of microorganisms in the case of the first enzyme of the sequence, 3-deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthetase. The comparative stability of the isoenzymes as well as the effect of aromatic amino acids in the growth medium upon the levels of the individual isoenzymes were shown for Salmonella typhimurium. Several lines of evidence are discussed to demonstrate the strong reliance of Escherichia coli upon the phenylalanine-sensitive isoenzyme for the ordinary biosynthetic needs of wild-type strains. The frequent occurrence of "dominant" isoenzyme species which resist repressive effects of the inhibitory end products was noted. The lack of an obligatory correlation of the level of an isoenzyme activity and the synthesis of the end product which specifically controls its activity is used to discount the possibility that each isoenzyme might feed a unique and separate metabolic pool of end-product precursor. An isoenzymic DAHP synthetase sensitive to feedback inhibition by low levels of tryptophan was fractionated from tyrosine- and phenylalanine-sensitive isoenzymes in cell-free extracts of Neurospora crassa.

Bacteria↗
PubMed1999

An unusual alkaline phosphatase isoenzyme associated with gastric carcinoma.

We describe a 50-year-old man with a diagnosis of gastric carcinoma made on gastroscopy after X-rays of the thoracolumbar spine had revealed multiple lytic metastases. A bone marrow aspirate showed adenocarcinoma cells. Polyacrylamide gel electrophoresis incorporating wheat germ lectin was used to separate the serum alkaline phosphatase isoenzymes. Isoenzyme separation showed a markedly increased amount of bone isoenzyme, a normal amount of liver isoenzyme and a considerable amount of an intestinal-like isoenzyme running cathodic to the bone isoenzyme. There was also some immunoglobulin-complexed alkaline phosphatase, which, when digested, showed more of the intestinal-like isoenzyme. This was a variant alkaline phosphatase isoenzyme found in a patient with a gastric carcinoma with a super bone scan. There have been two previous reports of patients with a variant alkaline phosphatase isoenzyme and a super bone-scan.

Alkaline Phosphatase↗