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At least 19 recordsLinked to original sources
PubMed1986

The indirect binding of triose-phosphate isomerase to myofibrils to form a glycolytic enzyme mini-complex.

Binding of triose-phosphate isomerase (D-glyceraldehyde-3-phosphate ketol-isomerase, EC 5.3.1.1) to muscle myofibrils depends upon the concurrent binding of either fructose-bisphosphate aldolase (EC 4.1.2.13), glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) or both of these enzymes together. Thus triose-phosphate isomerase does not bind directly to myofibrils but to glycolytic enzymes already bound to the myofibril. This was established using 125I-labelled enzymes, which are required to provide the necessary sensitivity for the measurement of the complex multiphasic adsorption isotherms. In the presence of aldolase, the most stable stoichiometric relationship is two aldolase bound per triose-phosphate isomerase. The results show that not all sites of aldolase or glyceraldehyde-3-phosphate dehydrogenase binding are available for triose-phosphate isomerase binding. Nevertheless, the results suggest the formation under particular circumstances of a minicomplex spanning the catalysis of fructose 1,6-bisphosphate to 3-phosphoglycerate. Such a complex could provide the physical basis of metabolic channeling in which metabolic intermediates are not released from the complex.

Animals↗
PubMed1987

Kinetic properties of triose-phosphate isomerase from Trypanosoma brucei brucei. A comparison with the rabbit muscle and yeast enzymes.

The kinetic properties of Trypanosoma brucei brucei triose-phosphate isomerase are compared with those of the commercially available rabbit muscle and yeast enzymes and with published data on the chicken muscle enzyme. With glyceraldehyde 3-phosphate as substrate Km = 0.25 +/- 0.05 mM and kcat = 3.7 X 10(5) min-1. With dihydroxyacetone phosphate as substrate Km = 1.2 +/- 0.1 mM and kcat = 6.5 X 10(4) min-1. The pH dependence of Km and Vmax at 0.1 M ionic strength is in agreement with the results published for the yeast and chicken muscle enzymes. At ionic strength below 0.05 M the effect of a charged group specific for the trypanosomal enzyme and absent from the yeast and rabbit muscle enzymes becomes detectable. This effect significantly increases Km whereas Vmax becomes slightly higher. Trypanosomal triose-phosphate isomerase is inhibited by sulphate, phosphate and arsenate ions, by 2-phosphoglycolate and a number of documented inhibitors in the same concentration range as are the other triose-phosphate isomerases. The trypanocidal drug, Suramin inhibits T. brucei and rabbit muscle triose-phosphate isomerase to the same extent while leaving the yeast enzyme relatively unaffected.

Animals↗
PubMed1992

Interconversion of D-fructose 1,6-bisphosphate and triose phosphates in human erythrocytes.

Aldolase and triose phosphate isomerase both display strict specificity towards the enantiomers of [1-3H]glycerone 3-phosphate. The enantiomer generated from D-[1-3H]glyceraldehyde 3-phosphate produces 3HOH in the aldolase reaction, whilst the other enantiomer generated from D-[3-3H]fructose 1,6-bisphosphate is solely detritiated in the reaction catalyzed by triose phosphate isomerase. Advantage was taken of such a specificity to assess, in human erythrocytes exposed to either D-[3-3H]glucose or D-[3,4-3H]glucose, the extent of D-glyceraldehyde 3-phosphate sequential conversion to glycerone 3-phosphate and D-fructose 1,6-bisphosphate, relative to net glycolytic flux. At 37 degrees C and in the presence of 5.6 mM D-glucose, only 55% of the metabolites of D-[4-3H]glucose underwent detritiation in the reactions catalyzed by triose phosphate isomerase and aldolase. Such a percentage was further decreased at low temperature (8 degrees C) or lower concentrations of D-glucose (0.2 and 1.0 mM). However, when the erythrocytes were exposed to menadione, the increase in 3HOH production from either D-[3-3H]glucose or D-[3,4-3H]glucose indicated that the majority of the 3H atoms initially located on the C4 of D-glucose were recovered as 3HOH upon circulation through the pentose phosphate pathway. These findings suggest that, under physiological conditions, a large fraction of D-glyceraldehyde 3-phosphate generated from exogenous D-glucose may undergo enzyme-to-enzyme channelling in the glycolytic pathway.

Blood Glucose↗
PubMed1985

Triose phosphate isomerase deficiency: prenatal diagnosis.

A child with triose phosphate isomerase deficiency has congenital nonspherocytic hemolytic anemia, mental subnormality, motor impairment, growth failure, and cardiac failure. The deficiency state is characterized by moderately reduced red cell triose phosphate isomerase activity and marked instability of the abnormal enzyme to heat. The stability characteristics of triose phosphate isomerase in cultured fibroblasts define the homozygous and heterozygous states with sufficient precision to allow prenatal diagnosis of the disorder. Successful prenatal identification of a heterozygote and an unaffected fetus in utero is described.

Amniocentesis↗
PubMed1974

Catalysis of pentose phosphate pathway reactions by cytoplasmic fractions from muscle, uterus and liver of the rat, and the presence of a reduced nicotinamide-adenine dinucleotide phosphate-triose phosphate oxidoreductase in rat muscle.

1. The enzymes of the pentose phosphate pathway were assayed in supernatant fractions from rat muscle, liver and uterus. 2. On incubation of ribose 5-phosphate with uterus and liver supernatants, triose phosphate, sedoheptulose 7-phosphate and hexose monophosphate accumulated. 3. When a muscle supernatant was used, glycerol 3-phosphate instead of triose phosphate appeared and there was a negligible accumulation of hexose monophosphate. 4. Hexose monophosphate production from ribose 5-phosphate was also followed by measuring NADP(+) reduction in the presence of an excess of phosphoglucose isomerase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. 5. With a muscle supernatant, NADPH was reoxidized as rapidly as it was formed owing to the presence of a NADPH-triose phosphate oxidoreductase. 6. A modification of the pentose phosphate pathway in skeletal muscle incorporating this enzyme is proposed.

Animals↗
PubMed1992

Reduction of trioses by NADPH-dependent aldo-keto reductases. Aldose reductase, methylglyoxal, and diabetic complications.

The substrate specificities of human aldose reductase and aldehyde reductase toward trioses, triose phosphates, and related three-carbon aldehydes and ketones were evaluated. Both enzymes are able to catalyze the NADPH-dependent reduction of all of the substrates used. Aldose reductase shows more discrimination among substrates than does aldehyde reductase and is generally the more efficient catalyst. The best substrate for aldose reductase is methylglyoxal (kcat = 142 min-1, kcat/Km = 1.8 x 10(7) M-1 min-1), a toxic 2-oxo-aldehyde that is produced nonenzymatically from triose phosphates and enzymatically from acetone/acetol metabolism. D- and L-glyceraldehyde and D- and L-lactaldehyde are also good substrates for aldose reductase. The aldose reductase-catalyzed reduction of methylglyoxal produces 95% acetol, 5% D-lactaldehyde. Further reduction of acetol produces only L-1,2-propanediol. Acetol and propanediol are two products that accumulate in uncontrolled diabetes. Both acetol and methylglyoxal were compared with glucose for their abilities to produce covalent modification of albumin. All three of these carbonyl compounds reacted with albumin to produce modified proteins with new absorption and emission bands that are spectrally similar. Both methylglyoxal and acetol are much more reactive than glucose. A new integrative model of diabetic complications is proposed that combines the aldose reductase/polyol pathway theory and the nonenzymatic glycation theory except that emphasis is placed both on methylglyoxal/acetol metabolism and on glucose metabolism.

Acetone↗
PubMed1985

Reaction of triosephosphate isomerase with L-glyceraldehyde 3-phosphate and triose 1,2-enediol 3-phosphate.

Triosephosphate isomerase catalyzes the isomerization and/or racemization reactions of L-glyceraldehyde 3-phosphate (LGAP), the enantiomer of the physiological substrate. The reaction is inhibited by the active site directed reagent glycidol phosphate. The amount of protonation product formation catalyzed by a fixed enzyme concentration is nearly independent of increasing steady-state concentrations of triose 1,2-enediol 3-phosphate caused by buffer catalysis of LGAP deprotonation. Therefore, enzymatic protonation of the enediol or enediolate, which could account for the observed enzymatic catalysis of LGAP isomerization and/or racemization, is at best a minor reaction. Instead LGAP reacts directly at the enzyme active site. Triosephosphate isomerase catalysis of the protonation of triose 1,2-enediol 3-phosphate was expected because of the strong evidence supporting an enediol reaction intermediate for the overall reaction catalyzed by isomerase. The most reasonable explanation for the failure to observe enzymatic protonation is that in solution the enediol undergoes beta elimination of phosphate (t 1/2 is estimated to be 10(-6) s) faster than it can diffuse to and form a complex with isomerase.

Animals↗
PubMed1991

The application of computational methods to the study of enzyme catalysis by triose-phosphate isomerase and stabilities of variants of bacteriophage T4 lysozyme.

We review our research on triose-phosphate isomerase and bacteriophage T4 lysozyme. In our studies over the last ten years we have used electrostatic potentials, computer graphics, quantum mechanics, molecular mechanics, molecular dynamics and free energy calculations to try to understand why triose-phosphate isomerase is such an efficient enzyme and why its efficiency is dramatically decreased by several site-specific mutations. For T4 lysozyme we have used free energy methods to analyse and try to understand why Thr-157----Val and Thr-157----Ala mutations decrease protein stability by about 1-2 kcal/mol.

Amino Acid Sequence↗
PubMed1986

Simple model for the effect of Glu165----Asp165 mutation on the rate of catalysis in triose phosphate isomerase.

We present an ab-initio self-consistent field calculation with a 4-31G basis set on a simple model for proton abstraction from hydroxyacetone (a model for dihydroxyacetone phosphate; DHAP) by formate, which is a model for Glu165 in triose phosphate isomerase. Earlier, we showed that the electrophilic groups on the enzyme (the NH3+ of Lys13 and the NH of His95) were essential to efficient catalysis by triose phosphate isomerase. These groups stabilized the enediolate formed by proton abstraction from the DHAP model so that proton transfer from this molecule to Glu165 became likely. In this study, we carry this analysis one step further. First, we re-examine the energy profile for proton transfer, using the fact that our earlier calculations showed that the combined effect of His95 and Lys13 on the reactant DHAP and intermediate enediolate was to make them equal in energy. Then, we analyze the likely effect of changing Glu165 to Asp165 and relate this to experiments on the kinetics of enzyme catalysis by the Glu165----Asp165 mutant.

Amino Acid Sequence↗
PubMed1975

The amino acid sequence of rabbit muscle triose phosphate isomerase.

The amino acid sequence of rabbit muscle triose phosphate isomerase was deduced by characterizing peptides that overlap the tryptic peptides. Thiol groups were modified by oxidation, carboxymethylation or aminoen. About 50 peptides that provided information about overlaps were isolated; the peptides were mostly characterized by their compositions and N-terminal residues. The peptide chains contain 248 amino acid residues, and no evidence for dissimilarity of the two subunits that comprise the native enzyme was found. The sequence of the rabbit muscle enzyme may be compared with that of the coelacanth enzyme (Kolb et al., 1974): 84% of the residues are in identical positions. Similarly, comparison of the sequence with that inferred for the chicken enzyme (Furth et al., 1974) shows that 87% of the residues are in identical positions. Limited though these comparisons are, they suggest that triose phosphate isomerase has one of the lowest rates of evolutionary change. An extended version of the present paper has been deposited as Supplementary Publication SUP 50040 (42 pages) at the British Library (Lending Division) (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms given in Biochem. J. (1975) 145, 5.

Amino Acid Sequence↗
PubMed1979

Enzyme-substrate and enzyme-inhibitor complexes of triose phosphate isomerase studied by 31P nuclear magnetic resonance.

The complex formed between the enzyme triose phosphate isomerase (EC 5.3.1.1.), from rabbit and chicken muscle, and its substrate dihydroxyacetone phosphate was studied by 31P n.m.r. Two other enzyme-ligant complexes examined were those formed by glycerol 3-phosphate (a substrate analogue) and by 2-phosphoglycollate (potential transition-state analogue). Separate resonances were observed in the 31P n.m.r. spectrum for free and bound 2-phosphoglycollate, and this sets an upper limit to the rate constant for dissociation of the enzyme-inhibitor complex; the linewidth of the resonance assigned to the bound inhibitor provided further kinetic information. The position of this resonance did not vary with pH but remained close to that of the fully ionized form of the free 2-phosphoglycollate. It is the fully ionized form of this ligand that binds to the enzyme. The proton uptake that accompanies binding shows protonation of a group on the enzyme. On the basis of chemical and crystallographic information [Hartman (1971) Biochemistry 10, 146--154; Miller & Waley (1971) Biochem. J. 123, 163--170; De la Mare, Coulson, Knowles, Priddle & Offord )1972) Biochem. J. 129, 321--331; Phillips, Rivers, Sternberg, Thornton & Wilson (1977) Biochem. Soc. Trans. 5, 642--647] this group is believed to be glutamate-165. On the other hand, the position of the resonance of D-glycerol 3 phosphate (sn-glycerol 1-phosphate) in the enzyme-ligand complex changes with pH, and both monoanion and dianon of the ligand bind, although dianion binds better. The substrate, dihydroxyacetone phosphate, behaves essentially like glycerol 3-phosphate. The experiments with dihydroxy-acetone phosphate and triose phosphate isomerase have to be carried out at 1 degree C because at 37 degrees C there is conversion into methyl glyoxal and orthophosphate. The mechanismof the enzymic reaction and the reasons for rate-enhancement are considered, and aspects of the pH-dependence are discussed in an Appendix.

Animals↗
PubMed1992

Simulations of the folding pathway of triose phosphate isomerase-type alpha/beta barrel proteins.

Simulations of the folding pathways of two large alpha/beta proteins, the alpha subunit of tryptophan synthase and triose phosphate isomerase, are reported using the knight's walk lattice model of globular proteins and Monte Carlo dynamics. Starting from randomly generated unfolded states and with no assumptions regarding the nature of the folding intermediates, for the tryptophan synthase subunit these simulations predict, in agreement with experiment, the existence and location of a stable equilibrium intermediate comprised of six beta strands on the amino terminus of the molecule. For the case of triose phosphate isomerase, the simulations predict that both amino- and carboxyl-terminal intermediates should be observed. In a significant modification of previous lattice models, this model includes a full heavy atom side chain description and is capable of representing native conformations at the level of 2.5- to 3-A rms deviation for the C alpha positions, as compared to the crystal structure. With a well-balanced compromise between accuracy of the protein description and the computer requirements necessary to perform simulations spanning biologically significant amounts of time, the lattice model described here brings the possibility of studying important biological processes to present-day computers.

Animals↗
PubMed1978

On the biochemical nature of triose- and hexose-stimulated insulin secretion.

The differential effects of several specific inhibitors of intermediary metabolism, mannoheptulose, 2-deoxylucose, and iodoacetate, were studied with isolated perifused pancreatic islets stimulated with glucose, mannose, glyceraldehyde, dihydroxyacetone, or alpha-ketoisocaproate. Insulin release rates and/or capacities to metabolize these caloric stimuli served as indicators of the inhibitors' actions. Mannoheptulose and 2-deoxyglucose blocked hexose-stimulated hormone release and hexose metabolism concomitantly, but left the functional and metabolic actions of trioses unaltered. Iodoacetate blocked hexose- and triose-stimulated hormone release as well as their metabolism in a parallel fashion. The action of alpha-ketoisocaproate was not affected by any of these three inhibitory agents. The data are most easily explained by a theory that incorporates metabolic signals, arising during the degradation of insulin-releasing fuel molecules, as an integral component in the process of beta-cell stimulation.

Animals↗
PubMed1989

The relationship between the (beta 1-3) N-acetylglucosaminyltransferase and the presence of oligosaccharides containing lacto-N-triose II structure in bovine and human milk.

We measured UDP-GlcNAc:Gal (beta 1-4) Glc (or GlcNAc) (beta 1-3) N-acetylglucosaminyltransferase activities in bovine (Holstein and Jersey cow) and human colostrums, and found in human colostrums sufficient activity to study the enzyme properties while not in bovine colostrums. The properties (requirements, pH optimum, acceptor specificity and Km values for lactose and N-acetyllactosamine) of the enzyme from human colostrum were very similar to those from human serum and urine. The reaction product was hydrolyzed by beta-N-acetylhexosaminidase, indicating that the N-acetylglucosaminyl residue was beta-linked to lactose. Methylation and hydrolysis of the reaction product from lactose [3H] labeled at the terminal galactose yielded 2, 4, 6-tri-O-methyl [3H] galactose. Thus the structure of the product was demonstrated to be GlcNAc (beta 1-3) Gal (beta 1-4) Glc (lacto-N-triose II). On the other hand, bovine sera contained N-acetylglucosaminyltransferase catalyzing the transfer of N-acetylglucosamine from UDP-GlcNAc to lactose. The enzyme activities were approximately 1/6-1/4 of that contained in human serum. The presence of (beta 1-3) N-acetylglucosaminyltransferase in human colostrum and its absence in bovine colostrums, apparently corresponds with the presence and absence of oligosaccharides containing lacto-N-triose II structure in colostrum.

Animals↗
PubMed1987

The regiochemistry and stereochemistry of the biosynthesis of vitamin B6 from triose units.

13C and 2H NMR spectroscopy has been employed to probe the biosynthesis of vitamin B6 in Escherichia coli. The 13C NMR spectrum of a sample of pyridoxol derived biosynthetically from D-[1,2,3,4,5,6-13C6]glucose shows that the bonds, C(2)-C(3) and C(4)-C(5), of the pyridine nucleus are the only two carbon-carbon bonds of pyridoxol which are generated de novo in the course of its biosynthesis from glucose. It follows that the pyridoxol skeleton is generated from two intact triose units and a triose-derived two-carbon unit, all of which are supplied by glucose. From the 2H NMR spectra of samples of pyridoxol derived from (R)-[1,1-2H2]glycerol and (S)-[1,1-2H2]glycerol, respectively, it can be deduced that the rehydroxymethyl group of glycerol enters C-2', C-4', and C-5' of the pyridoxol skeleton. It follows that each of the three fragments is derived from glycerol in stereo-specific fashion. These results answer questions concerning the regiochemistry and the stereochemistry of pyridoxol biosynthesis.

Carbon Isotopes↗
PubMed1977

12pter to 12p12.2: possible assignment of human triose phosphate isomerase.

Red cell triose-phosphate isomerase (TPI) was determined, together with other enzymes, in three patients with chromosome 12 abnormalities. In patient No. 1 (trisomy of the segment 12 pter leads to 12q 12) and in patient No. 2 (trisomy of the segment 12pter leads to 12p 12.1), the TPI activity was significantly increased. In patient No. 3 (deletion of the segment 12 p 11 leads to 12 p 12.2), the TPI activity was in the normal range. These results suggest that the human TPI locus is located on the chromosome 12 short arm, between 12p ter and 12 p 12.2.

Carbohydrate Epimerases↗
PubMed1991

Structure and expression of the triose phosphate isomerase (Tpi) gene of Drosophila melanogaster.

We report the isolation of the genomic sequence that encodes the enzyme triose phosphate isomerase of Drosophila melanogaster. There is a single copy of the Tpi sequence in the genome of Drosophila, as judged by Southern blots and in situ hybridization to salivary gland chromosomes. The sequence of 3414 nucleotides from the Tpi region was determined. The gene has an intron in the 5' untranslated region of the transcript and a second intron in the coding region at an evolutionarily conserved position. Transcripts initiate at a single site which does not have a TATA box in the usual position. Northern blot analysis of RNA prepared from different developmental stages revealed that Tpi mRNA is present in substantial amounts in oocytes, declines in abundance in early embryos, and begins to increase during mid-embryogenesis. Transcript abundance follows a pattern typical of enzymes involved in intermediate metabolism. A peak is found during third instar followed by a decline during pupal stages and then a second rise near the time of eclosion.

Animals↗
PubMed1988

Interpretation of triose phosphate isomerase isozymes in the cherimoya (Annona cherimola Mill.).

Detailed interpretation of triose phosphate isomerase (TPI) isozymes in seed plants has been restricted to only a few species. Three sets of TPI bands are regularly observed in the cherimoya (Annona cherimola), a primitive angiosperm. The slowest, set I, is expressed as one or three bands; the second-slowest set II, as one or two bands; and the fastest, set IV, as one or three bands. A faint set III, just cathodal to set IV, is detected rarely with overstaining. Set IV bands are expressed in macerated extracted pollen but not in pollen leachate. Dissociation-reassociation experiments reveal that the set II bands are heterodimers involving, in part, the enzymes involved in the set I bands. These data combined with those from full-sib progeny analysis lead us to propose a three-locus model to explain the TPI isozyme banding patterns in cherimoya. Sets I and IV consist of the allelic products of individual, single loci. Sets I and II occur in the cytoplasm. Set IV occurs in organelles. Set II isozymes are the intergenic heterodimers of the locus coding for set I and the locus coding for set III. Our results reported here are contrasted with the TPI isozyme patterns known for other vascular plants and suggest that the locus coding for set III may be a duplication of very ancient origin.

Carbohydrate Epimerases↗