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PubMed1994

Molecular abnormality of a unique Japanese glucose-6-phosphate dehydrogenase variant (G6PD Kobe) with a greatly increased affinity for galactose-6-phosphate.

Systematic molecular analysis of a Japanese class 1 glucose-6-phosphate dehydrogenase (G6PD) variant (G6PD Kobe) cDNA revealed a unique nucleotide substitution (1318 C to T) in exon 11, which predicts a substitution of leucine for phenylalanine at residue 440. This substitution is located in a region surrounding the putative structural NADP-binding domain. The markedly abnormal kinetics of glucose-6-phosphate (G6P) of G6PD Kobe suggest the interaction between both NADP and G6P binding sites.

Base Sequence↗
PubMed1989

Analysis by fast atom bombardment mass spectrometry of 4,4-dicarboxy-5-(pyridoxyl-5'-phosphate)-proline, of 4-carboxy-5-(pyridoxyl-5'-phosphate)-proline and 4,4-dicarboxy-5-pyridoxylproline.

gamma-Carboxyglutamic acid (Gla) reacts easily and quantitatively with piridoxal-5'-phosphate in H2O at room temperature, to give the 4,4-dicarboxy-5-(pyridoxyl-5'-phosphate)-proline (1). This product has been characterized by fast atom bombardment (FAB) mass spectrometry, including the B/E linked scan technique, ultraviolet and 1H nuclear magnetic resonance (NMR) analysis. In order to support further on the structure of 1, the 4-monodecarboxyderivative (2), obtained by heating compound 1 at 100 degrees C for 30 min and the 5'-dephosphoderivative (3), obtained by enzymatic hydrolysis of 1 with alkaline phosphatase, were also analysed by FAB and 1H NMR techniques. FAB was shown to be the only adequate ionization technique to deal with such thermolabile and non-volatile compounds and could provide an elegant and fast method to detect Gla in biological matrices.

Magnetic Resonance Spectroscopy↗
PubMed1988

Comparative studies on nephrotoxic effects of tris (2,3-dibromopropyl) phosphate and bis (2,3-dibromopropyl) phosphate on rat urinary metabolites.

The mechanism of Tris-BP or Bis-BP (a metabolite of Tris-BP) induced nephrotoxicity was investigated by determining urinary excretion of enzymes and selected metabolites. Rats received single oral doses of 0, 71.7, 143.4 and 286.8 mumol/kg tris (2,3-dibromopropyl) phosphate (Tris-BP) or bis (2,3-dibromopropyl) phosphate (Bis-BP). Urine was collected over a 24 h period and subjected to biochemical examinations. Comparative studies on Tris-BP- and Bis-BP-induced nephrotoxicities were carried out for abnormal patterns of urinary excretion. The urinary excretion of glucose was higher in Bis-BP than Tris-BP at a dose of 143.4 mumol/kg, but this pattern reversed at a dose of 286.8 mumol/kg. Peak lactate excretion occurred later than peak glucose excretion with 143.4 and 286.8 mumol/kg Tris BP and 143.4 mumol/kg Bis-BP. Bis-BP 286.8 mumol/kg caused a transient urinary elevation of lactate on Day 2. Uric acid was excreted at higher levels for Bis-BP than Tris-BP on day 2 of urine collection. Activities of urinary enzymes including alkaline phosphatase, aspartate aminotransferase and gamma-glutamyltransferase, were different on the first day of post-treatment for Tris-BP and Bis-BP. Leucine aminopeptidase and lactate dehydrogenase levels differed on the second day. Activities of the former enzymes on the day 2 urine suggested a transformation of Tris-BP to Bis-BP. Urinary patterns of lactate dehydrogenase isoenzymes (LDH-1-LDH-5) were different between Tris-BP and Bis-BP when rats were treated with the dose of 286.8 mumol/kg: Tris-BP caused a higher excretion of LDH-4 and LDH-5 in urine on day 1 and all five isoenzymes into the day 2 urine. Bis-BP caused slightly higher excretion of LDH-5 and LDH-4 into the day 1 and 3 urine, respectively. Bis-BP but not Tris-BP caused abnormally urinary excretion of sodium ion. Histopathologically, the nephrotoxic effect of Tris-BP appeared one day later and was more obvious than that of Bis-BP in rats after single oral administration.

Animals↗
PubMed1986

Fructose-6-phosphate is not a substrate for glucose-6-phosphate dehydrogenase.

D-Fructose-6-phosphate was shown not to be a substrate for glucose-6-phosphate dehydrogenases (EC. 1.1.1.49) from human erythrocytes, bovine adrenal, rat liver, three yeasts (brewer's yeast, baker's yeast, and Candida utilis), and Leuconostoc mesenteroides. These findings contrast with those of G.M. Kidder (J. Exp. Zool., 226:385-390, '83).

Adrenal Glands↗
PubMed2000

Molecular cloning and expression of the mouse N-acetylneuraminic acid 9-phosphate synthase which does not have deaminoneuraminic acid (KDN) 9-phosphate synthase activity.

A cDNA of the mouse homologue of Escherichia coli N-acetylneuraminic acid (Neu5Ac) synthase (neuB gene product) was cloned by the PCR-based method. The mouse homologue consists of 359 amino acids, and the cDNA sequence displays 33% identity to that of the E. coli Neu5Ac synthase. The recombinant mouse homologue which is transiently expressed in HeLa cells does not exhibit the Neu5Ac synthase activity, which catalyzes condensation of phosphoenolpyruvate (PEP) and N-acetylmannosamine (ManNAc) to synthesize Neu5Ac, but the Neu5Ac 9-phosphate (Neu5Ac-9-P) synthase activity, which catalyzes condensation of PEP and ManNAc 6-phosphate (ManNAc-6-P) to synthesize Neu5Ac-9-P. Thus, the mouse homologue of E. coli Neu5Ac synthase is the Neu5Ac-9-P synthase. The Neu5Ac-9-P synthase is a cytosolic enzyme and ubiquitously distributed in mouse various tissues. Notably, the Neu5Ac-9-P synthase can not catalyze the synthesis of deaminoneuraminic acid (KDN) or KDN-9-P from PEP and Man or ManNAc-6-P, thus suggesting that the enzyme is not involved in the synthesis of KDN. This is consistent with the previous observation that only a very low activity to synthesize KDN is found in mouse B16 cells [Angata, T., et al. (1999) Biochem. Biophys. Res. Commun. 261, 326-331].

Amino Acid Sequence↗
PubMed1991

L-ascorbic acid 2-phosphate, a phosphate derivative of L-ascorbic acid, enhances the growth of cultured rabbit keratocytes.

We examined the effect of L-ascorbic acid 2-phosphate (P-Asc) on the proliferation of cultured rabbit keratocytes. P-Asc is a phosphate derivative of L-ascorbic acid and has more prolonged vitamin C activity in solution than does L-ascorbic acid. The proliferation of cultured keratocytes was promoted by the presence of P-Asc in culture medium. Transmission electron microscopic observations revealed that cells were more multi-layered after culture in the presence of P-Asc (0.1 mM) for 30 days than were those cultured in the absence of P-Asc. The effect of P-Asc was abrogated by L-azetidine 2-carboxylic acid, which is an analogue of proline that inhibits the production and secretion of collagen. Our observations support a therapeutic role for P-Asc in the repair of corneal stromal damage such as that caused by a corneal chemical burn.

Animals↗
PubMed1983

Regulation of the oxidative phase of the pentose phosphate cycle in Aspergillus oryzae (Ahlburg). I. Induction of glucose-6-phosphate dehydrogenase.

The activity of glucose-6-phosphate dehydrogenase changes when the mycelium is grown on different carbon sources. In the presence of ribose, the activity of the enzyme is approximately 3 times higher than when the mycelium is grow in a medium containing glucose. This increase in the enzyme activity is developed progressively when the concentration of ribose increases from 1% to 6% and it is blocked if cycloheximide is added to the medium. This results suggest an increase in "de novo" synthesis of the enzyme rather than an specific activation of the latent enzyme. Three isoenzymes of glucose-6-phosphate dehydrogenase are isolated from mycelium grown on ribose, whereas only two isoenzymes are isolated from mycelium grown on glucose.

Aspergillus↗
PubMed1981

Serine phosphate, threonine phosphate and gamma-carboxyglutamic acid in normal and experimentally induced, pathologically calcified rat skin (topical cutaneous calciphylaxis).

The amount of non-collagenous proteins is increased greatly during the pathological calcification of rat skin experimentally induced by dihydrotachysterol (DHT) and Ovalbumin (topical cutaneous calciphylaxis). This is accompanied by an increase in the total amount and concentrations of protein-bound serine phosphate [Ser(P)], threonine phosphate [Thr(P)] and gamma-carboxyglutamic acid (Gla), almost all of which can be extracted from the tissue and can be dissociated from collagen in 0.5M EDTA. The EDTA-soluble, non-collagenous proteins are rich in aspartic and glutamic acids, similar to the non-collagenous, EDTA-soluble proteins of bone, cementum and calcified cartilage, and quite distinct from those of dentin and enamel.

1-Carboxyglutamic Acid↗
PubMed1991

Effects of ethinyl oestradiol/polyoestradiol phosphate and estramustine phosphate on some proteins related to haemostasis in prostatic carcinoma patients.

Twenty-four previously untreated patients with carcinoma of the prostate were prospectively randomized to one of the following treatments: (1) ethinyl oestradiol combined with polyoestradiol phosphate (EE/EP); (2) estramustine phosphate (EM); (3) bilateral orchiectomy. The effects on some plasma proteins related to haemostasis were studied by measuring the concentrations of alpha-1-antitrypsin, orosomucoid, haptoglobin, antithrombin III, C1-inhibitor and von Willebrand's factor before and 3 months after the start of treatment. Orchiectomy induced a reduction of alpha-1-antitrypsin and haptoglobin, while the other studied proteins were unaffected. It was found that both EE/EP and EM treatment induced significant decreases of orosomucoid, haptoglobin, antithrombin III and C1-inhibitor, while the same treatment increased the plasma concentration of alpha-1-antitrypsin. None of these treatments showed any influence on the plasma concentration of the von Willebrand factor. No differences were observed between EE/EP and EM for any of the studied proteins, suggesting comparable oestrogenic effects of these forms of treatment in patients with prostatic carcinoma. The findings are discussed in relation to the proposed difference in thromboembolic complications between EE/EP and EM treatments of prostatic carcinoma patients.

Aged↗
PubMed1982

Coordinate regulation of the pentose phosphate pathway and of the activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase (decarboxylating).

The activities of glucose-6-phosphate dehydrogenase (GPD) and 6-phosphogluconate dehydrogenase (decarboxylating) (PGD) in Saccharomyces cerevisiae were found to change by a factor similar to the reported changes in the rate of the pentose phosphate pathway between cells grown in minimal medium and in rich medium. It is suggested that the rate of this pathway is regulated not only by the activity of GPD, a well-known key enzyme, but also by PGD. These two enzymes seem to function in a coordinated fashion.

Amino Acids↗
PubMed2005

Formaldehyde activating enzyme (Fae) and hexulose-6-phosphate synthase (Hps) in Methanosarcina barkeri: a possible function in ribose-5-phosphate biosynthesis.

Formaldehyde activating enzyme (Fae) was first discovered in methylotrophic bacteria, where it is involved in the oxidation of methanol to CO2 and in formaldehyde detoxification. The 18 kDa protein catalyzes the condensation of formaldehyde with tetrahydromethanopterin (H4MPT) to methylene-H4MPT. We describe here that Fae is also present and functional in the methanogenic archaeon Methanosarcina barkeri. The faeA homologue in the genome of M. barkeri was heterologously expressed in Escherichia coli and the overproduced purified protein shown to actively catalyze the condensation reaction: apparent Vmax = 13 U/mg protein (1 U = micromol/min); apparent Km for H4MPT = 30 microM; apparent Km for formaldehyde = 0.1 mM. By Western blot analysis the concentration of Fae in cell extracts of M. barkeri was determined to be in the order of 0.1% of the soluble cell proteins. Besides the faeA gene the genome of M. barkeri harbors a second gene, faeB-hpsB, which is shown to code for a 42 kDa protein with both Fae activity (3.6 U/mg) and hexulose-6-phosphate synthase (Hps) activity (4.4 U/mg). The results support the recent proposal that in methanogenic archaea Fae and Hps could have a function in ribose phosphate synthesis.

Aldehyde-Lyases↗
PubMed1985

Determination of picomole amounts of glycerate 3-phosphate, glycerate 2-phosphate, and phosphoenol pyruvate by an enzymatic assay coupled to firefly luciferase/luciferin luminescence.

A procedure for the determination of picomole amounts of glycerate 3-phosphate, glycerate 2-phosphate, and phosphoenol pyruvate is described. These metabolites were utilized by the glycolytic enzymes phosphoglycerate mutase, enolase, and pyruvate kinase to generate ATP which was determined by firefly luciferase/luciferin luminescence. The phosphoglycerate mutase used was of the glycerate 2,3-bisphosphate-independent type and was prepared from wheat germ. Stoichiometric conversion of glycerate 3-P, ranging in amount from 9 to 275 pmol, occurred after 25 min preincubation and required a narrow range of added mutase. The application of the procedure for determining these metabolites in suspensions of plant protoplasts is described.

Adenosine Diphosphate↗
PubMed1991

Amplified colorimetric assay of alkaline phosphatase using riboflavin 4'-phosphate: a simple method for measuring riboflavin and riboflavin 5'-phosphate.

Alkaline phosphatase hydrolyzes riboflavin 4'-phosphate to produce riboflavin. This is converted to riboflavin 5'-phosphate, using riboflavin kinase, which reconstitutes apoglycolate oxidase to give hologlycolate oxidase. This enzyme catalyzes the oxidation of glycolate with simultaneous production of hydrogen peroxide which is detected via the formation of a colored product through the action of peroxidase. The system allows the detection of 4 amol after a 2-h incubation.

Alcohol Oxidoreductases↗
PubMed1989

Dihydroxyacetone phosphate acyltransferase and alkyldihydroxyacetone phosphate synthase activities in rat liver subcellular fractions and human skin fibroblasts.

Dihydroxyacetone phosphate acyltransferase (DHAP-AT) and alkyldihydroxyacetone phosphate synthase (DHAP-synthase) activities were examined in subcellular fractions of rat liver. The results indicate that at least 80% of DHAP-AT (assays carried out at pH 5.4) activity in rat liver is in peroxisomes, and the remaining activity is mitochondrial. In contrast to DHAP-AT, DHAP-synthase was detected in all subcellular fractions analyzed but the activity in peroxisomes was 208-fold and 42-fold greater compared to mitochondria and microsomes, respectively. We estimate that at least 70% of the DHAP-synthase activity in rat liver is in peroxisomes. DHAP-AT and DHAP-synthase activities were also examined in homogenates of skin fibroblasts from patients with inherited defects in peroxisomal structure and/or function. Both the enzyme activities were deficient in Zellweger syndrome whereas the activities were only partially deficient in infantile Refsum's disease. Greater reduction in DHAP-synthase activity, but only a partial reduction in DHAP-AT activity was observed in rhizomelic chondrodysplasia punctata. However, both DHAP-AT and DHAP-synthase activities were either normal or near normal in Refsum's disease or X-linked adrenoleukodystrophy. The results reported suggest that various peroxisomal disease states can be identified based on DHAP-AT and DHAP-synthase activities in skin fibroblasts of patients.

Acyltransferases↗
PubMed1980

Adenylate cyclase in silkworm. Effects of adenosine 3'-phosphate and 2'-deoxyadenosine 3'-phosphate on the enzyme system in fat body.

Adenosine 3'-phosphate and 2'-deoxyadenosine 3'-phosphate inhibit silkworm fat body adenylate cyclase. The inhibition has a rapid onset, and is dependent on the concentration of Mn2+ or Mg2+. The concentrations of 2'-deoxy-3'-AMP required for 50% inhibition (Ki) are 13 microM with 2 mM Mn2+ and 32 microM with 10 mM Mg2+. These Ki values are 7-30 times lower than that for 2'-deoxyadenosine. Stimulation of adenylate cyclase by NaF renders the activity more sensitive to the nucleotide inhibition, reducing the Ki value to 4 microM in the presence of Mn2+. The inhibitory activity is specific for adenine 3'-nucleotide; Ki for 2'-AMP and 5'-AMP are ten times or more higher than that for 3'-AMP, and the other 3'-nucleotides including 8-bromo-3'-AMP, 3'-IMP and 3'-GMP have little or no inhibitory activity.

Adenosine Monophosphate↗
PubMed1976

The crystal and molecular structure of the polymeric complex of zinc(II) withcytosine 5'-phosphate: metal bonding to both N(3) and phosphate.

Crystal structure analysis of the zinc(II) complex with cytosine 5'-phosphate, (C9H12N3O8P)Zn(H2O), shows that the complex is two-dimensionally polymeric, and the zinc atom is tetrahedrally coordinated to N(3) of the pyrimidine, to two phosphate oxygen atoms and to one water molecule. The zinc atom also forms weak intramolecular interaction with O(2) of the pyrimidine.

Cytosine Nucleotides↗
PubMed1984

Metabolism in vitro of tris(2,3-dibromopropyl)-phosphate: oxidative debromination and bis(2,3-dibromopropyl)phosphate formation as correlates of mutagenicity and covalent protein binding.

Tris(2,3-dibromopropyl)phosphate (Tris-BP) was found to be metabolized by liver microsomes obtained from untreated and phenobarbital-pretreated rats. Metabolites of Tris-BP, whose formation was dependent on NADPH and oxygen, included bromide ion and bis(2,3-dibromopropyl)phosphate (Bis-BP). The rates of formation of these metabolites were markedly increased in liver microsomes isolated from phenobarbital-pretreated rats compared to microsomes from untreated rats. In the presence of either SKF 525-A or metyrapone, the formation rates of bromide ion and Bis-BP were decreased, whereas alpha-naphthoflavone had no effect. The effects of the various treatments on bromide release and Bis-BP formation paralleled those that have been previously observed with respect to the activation of Tris-BP to mutagenic and covalently protein bound metabolites. Furthermore, rates of oxidative debromination of several Tris-BP analogs directly correlated with their respective mutagenicities. Addition of glutathione (GSH) to microsomal incubations of Tris-BP increased bromide release substantially over control, values but had no effect on Bis-BP formation. On the other hand, the addition of GSH to microsomes decreased covalent binding and mutagenicity of Tris-BP with increased formation of water soluble metabolites. GC/MS analysis of ethyl acetate extracts from incubations of rat liver microsomes with Tris-BP identified 2-bromoacrolein (2-BA) as a metabolite. Introducing deuterium at the carbon atom number 1 of the propyl moiety of Tris-BP had no effect on either bromide release or mutagenicity, whereas the analog labelled at carbon atom 3 showed significant isotope effects on both activities. In contrast, deuterium substitution at carbon atom 2 gave a significant isotope effect on bromide release, but not on mutagenicity. The data indicate that Tris-BP can be metabolized by rat liver microsomes to Bis-BP and 2-bromoacrolein catalyzed by cytochrome P-450 in a process liberating bromide ions. Further, the results are consistent with oxidation at the terminal carbon atom of Tris-BP thereby forming 2-bromoacrolein, which is postulated to be the metabolite mainly responsible for Tris-BP mutagenicity.

Animals↗