The Role of the Tyrosyl Groups on the Mechanism of Action of Chicken Heart Lactic Dehydrogenase^*

Abstract

BIOCHEMISTRY 2288thioester and an associate oxidation-reduction cofactor (e.g., NAD), neither of which is dissociable from the enzyme surface. This proposal would require either two different reversible, direct, stereospecific hydride transfers or one reversible, direct, nonspecific hydride transfer. The direct internal hydride shift proposal is considered most likely at this time since it is analogous with the glyoxalase model system.

Factors in the Iodination of Histidine in Proteins

“…Nearly all the tyrosyl residues of lactic dehydrogenase were iodinated (24 of 26 residues). This agrees with results obtained by Dubc et al. [i7] who iodinated up to 21 residues/mole, but is distinctly more than reported by DiSabato [5]. Neither of these workers reported iodohistidine formation whereas about 5 such residues were iodinated under our conditions.…”

“…who iodinated up to 21 residues/mole, but is distinctly more than reported by DiSabato [5]. Neither of these workers reported iodohistidine formation whereas about 5 such residues were iodinated under our conditions.…”

“…Indirect evidence for the iodination of histidyl residues in proteins was adduced long ago by Bauer and Strauss [l] for globin and by Fraenkel-Conrat [2] for lysozyme. More recently, the decrease of histidyl residues in hydrolysates of iodoproteins has been taken as evidence that iodohistidyl residues had been formed 13-61, and it is generally held that iodohistidines are destroyed during acid hydrolysis [2, 3,5,6]. It is well established, although not generally appreciated, that mono-and diiodohistidyl residues are readily formed during the iodination of a variety of proteins in vitro.…”

Identification of a nucleic acid helix-destabilizing protein from rat liver as lactate dehydrogenase-5.

“…33). Diazotization of this tyrosine residue with sulfanilic acid or iodination abolishes LDH activity (34,35). On the other hand, nitration of tyrosine-238 seems to have a more pronounced effect on the ability of HDP/LDH to act as a ss DNA binding protein in vitro than on its ability to act as a dehydrogenase.…”

Aminoacid Sequence of Dogfish M 4 Lactate Dehydrogenase

“…The sequences of the N-terminal 18 residues of dogfish M4 lactate dehydrogenase (1), of several small peptides from pig H4 lactate dehydrogenase (17), and of a peptide containing an essential histidine residue have been reported (11,18). Preliminary evidence for involvement of one, and possibly as many as three, arginine residues (19) and of one tyrosine residue (20,21) per subunit in enzymatic activity has been presented.…”