Structural adaptations of lactate dehydrogenase isozymes.

Abstract

The three-dimensional structures of dogfish M4 (muscle) and pig H4 (heart) lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) have been determined and correlated with the amino acid sequences of the dogfish M4, pig M4, pig H4, chicken M4, and chicken H4 lactate dehydrogenase isozymes. These results have been related to the known differences of physicochemical properties between the M and H lactate dehydrogenase isozymes. By far the largest structural alterations occur in the transition between the "apo" and "ternary complex" conformational states of the enzyme rather than between species or isozymes. The major catalytic difference can be explained by a replacement of alanine (in the M chain) with a glutamine (in the H chain) in the vicinity of the binding site of the coenzyme phosphates. The known immunological differentiation of the M and H isozymes is consistent with the differences in their amino acid sequences.The subunits of lactate dehydrogenase (LDH; L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) exist as two major structural forms, usually referred to as M (muscle) and H (heart) or A and B, respectively, which give rise to five different isozymes of the tetrameric molecule (1, 2) in higher vertebrates. The differences in the properties of the LDH isozymes are dependent on their subunit composition and are most exaggerated between the homotetramers M4 (LDH-5) and H4 (LDH-1). The most important of these differences are (independent of species): (i) The turnover number of the M4 isozyme is generally about twice that for the H4 isozyme (3-5).(ii) The activity of the H4 isozyme is more readily diminished by modification of the carboxyamide group on the 3 position of the nicotinamide (6). For instance, acetylpyridine adenine dinucleotide reduces the rate of catalysis by at least five when compared to NAD in the H4 enzyme, whereas the M4 isozyme is not especially sensitive to this difference of the NAD molecule (7). (iMi) The forward reaction lactate-to-pyruvate is inhibited to a far greater extent by high concentrations of pyruvate in the H4 than in the M4 isozyme (5, 7-9). (iv) Both the enzymic activity and the affinity of the substrate for enzyme are reduced to a greater extent in the M4 isozyme as the length of the aliphatic chain of the a-keto acid increases (10-12). (v) The H4 isozyme binds oxidized or reduced coenzyme better than the M4 isozyme (13-20). (vi) An antiserum induced in rabbit against the M4 isozyme of one species will crossreact with the M4 isozyme from several closely related species but not with the H4 isozyme of the same species (4,(21)(22)(23)(24)(25). Some appreciation of these differences is now possible from a correlation of recent studies on three-dimensional and primary structures of the H4 and M4 LDH isozymes.The tertiary structure of dogfish M4 LDH has been determined independently for the apo-enzyme and for a complex of LDH, coenzyme, and substrate analogue. The apo-enzyme has been studied at 2.0-A resolution, while a series of isomorphous ternary complexes h...

Malate dehydrogenase: A model for structure, evolution, and catalysis

“…The following complete MDH amino acid sequences were available: maize (Metzler et al, 1989); sorghum (Luchetta et al, 1991); pig (c) (Birktoft et al, 1989b); mouse (c) (Setoyama et al, 1988); T. fluvus (Nishiyama et al, 1986); S. typhimurium (Lu & Abdelal, 1993); E. coli (McAlister-Henn et al, MDHs (Grant et al, 1987); pig (m) (Birktoft & Banaszak, 1987); mouse (m) (Takeshima et al, 1988); rat (m) 1984); watermelon (Gietl et al, 1990); yeast (Minard & McAlister-Henn, 1991); H. marismortui (Cendrin et al, 1993). The LDH sequences used were rabbit chain" (Sass et al, 1989) and dogfish chain" (Eventoff et al ., 1977) and B. stearothermophilus LDH (Barstow et al, 1986 …”

First case of missense mutation (LDH-H:R171P) in exon 4 of the lactate dehydrogenase gene detected in a Japanese patient

“…The importance of the amino acid Arg at residue 171 in LDH-H is shown by its almost absolute conservation among six vertebrates (Takano et al 1989;Hiraoka et al 1990;Eventoff et al 1977;Chung et al 1985;Li et al 1985; (Fig. 2).…”

The l‐lactate dehydrogenase gene of the hyperthermophilic bacterium Thermotoga maritima cloned by complementation in Escherichia coli

“…The GC content of 48.6% (for all triplets) is much lower than one Piontek et al, 1990. Numbering according to Eventoff et al (1977). In the native tetrameric quaternary structure, the active-site loop connecting with aD/E (marked in black) points to the solvent accessible periphery of the molecule.…”

“…In this communication, we report the molecular cloning of the gene and the expression of the enzyme. Comparing the amino acid sequence (derived from the nucleotide sequence of the gene) with the primary structures of LDH species from other sources, it becomes clear that there is a high similarity, suggesting the topology of the enzyme to be similar to those determined for mesophilic enzymes (Holbrook et al, 1975;Eventoff et al, 1977;Schar et al, 1982).…”