Muscle triosephosphate isomerase

T. aquaticus, and comparison of this sequence with that of the lobster muscle enzyme shows a sequence identity of 50% which is again significantly higher than was found in comparison of bacterial and liver alcohol dehydrogenase (33) or bacterial and muscle triosephosphate isomerase (SP). 

Compound V or glycidol phosphate was used by Rose and O Connell (1969) to study muscle triosephosphate isomerase because it closely resembles the presumed ene-diol intermediate in this enzyme s reaction mechanism. Coincidentally, it also proved to be an effective inhibitor of enolase even though it is not closely analogous to substrates of this enzyme. The structure of glycidol phosphate is similar to phosphononomycin (DC), an antibiotic isolated from fermentation broths of Streptomyces fradiae (Christensen et al. 1969). 

Based on the pH dependency of the inactivation rate of rabbit muscle triosephosphate isomerase with glycidol phosphate, the pK for Glu-165 was calculated to be less than 5.5 in one study and 6.0 in another. Since this difference could be due to the complication of a variable affinity of the reagent for the enzyme as a result of the change in ionization state of the reagent over the pH range examined, the pH dependency of inactivation rate was also studied with the strong, monoprotic acid chloroacetol sulfate, another compound which selectively esterifies Glu-165. With this compound, the pK of Glu-165 in the rabbit muscle enzyme was found to be less than 5.0. An exact value could not be determined because of the instability of the enzyme to acid however, with the more stable yeast enzyme, a pKa of 3.9 was calculated. Thus, the acidity of the essential carboxyl group is consistent with its postulated role in catalysis. 

Table 4.1 The amino acid residues of the eight parallel p strands in the barrel structure of the enzyme triosephosphate isomerase from chicken muscle...

Barton-Davis ER, Cordier L, Shotrrrma Dl, Leland SE, Sweeney HL (1999) Aminoglycoside antibiotics restore dystrophin function to skeletal muscles of mdx mice. J Clin Invest 104 375-381 Belgrader P, Cheng J, Maquat LE (1993) Evidence to implicate translation by ribosomes in the mechanism by which nonsense codons reduce the nuclear level of human triosephosphate isomerase mRNA. Proc Natl Acad Sci USA 90 482 86... 

Triosephosphate isomerase Origin rabbit muscle Biozyme... 

Lambeir, A.-M., Opperdoes, F. R. and Wierenga, R. K. (1987) Kinetic properties of triosephosphate isomerase from Trypanosoma brucei a comparison with the rabbit muscle and yeast enzymes. Eur. J. Biochem. 168 69-74. 

In the case of pyruvate kinase from cat muscle, too, the folding patterns of the domains could be compared with those of other proteins. Of the three domains in this protein (A, B, and C) similarities were noted between A and the structtire of triosephosphate isomerase and between C and the nucleotide binding region of lactate dehydrogenase. 

The most successful application of haloacetol phosphates as affinity labels has been in the partial characterization of the active site of triosephosphate isomerase. Very similar studies, carried out independently in the laboratories of F. C. Hartman and J. R. Knowles, demonstrated an essential glutamyl y-carboxylate (esterified by the reagent) in the enzyme. The recently determined primary structure of the enzyme from rabbit muscle places the glutamyl at position 165. All the usual criteria of affinity labeling were satisfied and have been well documented. Certain aspects of these studies that either relate to the use of haloketones in general or have provided evidence of the carboxylate s intimate role in the catalytic process will be considered. 

In 1934 dialyzed extracts of muscle and yeast were found to catalyze the cleavage of fructose diphosphate to dihydroxyacetone phosphate. A closer examination of this reaction revealed that instead of catalyzing the formation of dihydroxyacetone phosphate, the enzyme split fructose diphosphate to equal amounts of dihydroxyacetone phosphate and d-3-phosphoglyceraldehyde. This conclusion was based on the observations that (1) in the process of purifying aldolase, triosephosphate isomerase is removed and hence triosephosphates accumulate with no further change and (2) trapping agents, such as cyanide, hydrazine, and sulfite, will effec-... 

In 1934 it was shown that yeast and mammalian muscle contain an enz3rme aldolase) which splits this fructose-l-6-diphosphate between carbon atoms 3 and 4 to give triose phosphates (glyceraldehyde-3-phosphate and dihydroxyacetone phosphate). The same enzyme was, by 1949, shown to be universally distributed in higher plants. Further, the two isomeric triosephosphates formed are interconvertible by means of a second enzyme, phosphotriose isomerase. This is important because it is only the glyceraldehyde-3-phosphate which is normally further metabolised in respiration. 

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