A reactive histidine residue at the active site of pig heart mitochondrial malate dehydrogenase

Physicochemical properties of pig and horse heart mitochondrial malate dehydrogenase.

A glutamyl residue in the active site of triphosphopyridine nucleotide-dependent isocitrate dehydrogenase of pig heart.

The maximum velocity of the reaction catalyzed by the pig heart TPN-specific isocitrate dehydrogenase depends on the basic form of an enzymatic group of pK 5.7. This pK is independent of temperature from 10-30” and increases in 20% ethanol, suggesting the ionization of a carboxyl group. The enzyme is inactivated by incubation at pH 7.0 with 1 cyclohexyl3 (2 morpholinoethyl) carbodiimide either ...

Studies on the presence and role of tryptophan in pig heart mitochondrial malate dehydrogenase.

Several different experimental approaches have shown the presence of tryptophan in malate dehydrogenase from pig heart mitochondria. The methods used were (a) fluorescence measurement of tryptophan content after acid hydrolysis and separation of amino acids by paper chromatography, (b) recovery of tryptophan labeled with tritium after incubation of the enzyme with tritiated substrates, (c) dete...

Demonstration of the presence of a histidine residue at the active site of streptococcal proteinase.

Experiments are described which have led to the selective alkylation of a histidine residue in streptococcal proteinase without concomitant reaction with the single essential sulfhydry1 group. The reduced, active form of the enzyme was first treated with sodium tetrathionate to protect the sulfhydry1 group and to introduce a negative charge near the active center. The resulting inactive derivat...

Malate dehydrogenase, inhibition of pig heart supernatant enzyme by iodoacetamide.

Pig heart supernatant malate dehydrogenase is alkylated by 250 mM iodoacetamide at 37 degrees C in pH 7.5 Tris/acetate buffer which is 0.05 M with respect to acetate to form enzyme with 1,3-dicarboxamidomethyl histidine, 3-carboxamidomethyl histidine, 1-carboxamidomethyl histidine, carboxamidomethyl cysteine, and carboxamidomethyl methionine. 1,3-Dicarboxamidomethyl histidine forms with a stoic...