Occurrence and Properties of Lactic Dehydrogenases of Fermentative Mycoplasmas

Abstract

Eight fermentative mycoplasmas differing in genome size, deoxyribonucleic acid (DNA) base composition, or sterol dependence were examined for lactic dehydrogenase composition by spectrophotometric assay and polyacrylamide gel electrophoresis. Three completely different patterns of lactic dehydrogenase composition were found. (i) A nicotinamide adenine dinucleotide (NAD)-dependent L(+)-lactic dehydrogenase was found in Mycoplasma pneumoniae, M. gallisepticum, M. mycoides var. mycoides, mycoplasma UM 30847, M. neurolyticum, and Acholeplasma axanthum. Electrophoresis of cell-free extracts of each of these mycoplasmas produced, with the exception of M. mycoides var. mycoides and UM 30847, single, different enzyme bands. M. mycoides var. mycoides and UM 30847 were similar and formed multiple bands of enzyme activity. We were unable to establish whether these multiple bands were due to lactic dehydrogenase isoenzymes or artifacts. (ii) An NAD-dependent D(-)lactic dehydrogenase which could not be reversed to oxidize lactate was found in M. fermentans. (iii) A. laidlawii A possessed an NAD-independent D(-)lactic dehydrogenase capable of reducing dichlorophenol-indophenol, and an NAD-dependent L(+)-lactic dehydrogenase which is specifically activated by fructose-1, 6-diphosphate. Heretofore, this enzyme regulatory mechanism was known to occur only among the Lactobacillaceae. No yeast-type lactic dehydrogenase activity was found in any of the mycoplasmas examined. The stereoisomer of lactic acid accumulated during growth correlated perfectly with the type of NAD-dependent lactic dehydrogenase found in each mycoplasma. The types of lactic dehydrogenase activity found in these mycoplasmas were not related to genome size, DNA base composition, or sterol dependence.of the fermentative mycoplasmas, we searched 633 on July 31, 2020 by guest

Properties of a Fructose-1, 6-Diphosphate-Activated Lactate Dehydrogenase from Acholeplasma laidlawii Type A

“…The enzyme is specific for the L(+)-stereosiomer of lactic acid. As reported previously, only L( + )-lactic acid is formed from pyruvate (11). This was confirmed under conditions, described below, where it was possible to reverse the reaction and obtain oxidation of L(+)-lactate only and not D(-)-lactate.…”

“…The number of proteins in the partially purified enzyme preparation was estimated by polyacylamide gel electrophoresis. Electrophoresis in 7.5% gels was carried out as described previously (11); gels were stained with 0.25% Coomassie blue and destained in 7% acetic acid.…”

“…The FDP-activated LDHs of A. laidlawii and the lactic acid bacteria may have molecular similarities, since aL have binding sites for the three ligands pyruvate, FDP, and reduced nico-tinamide adenine dinucleotide (NADH). These LDHs may thus be useful in examining evolutionary relations between mycoplasmas and the lactic acid bacteria (11).…”

Origins of the mycoplasmas: sterol-nonrequiring mycoplasmas evolved from streptococci

“…Samples were stored at -20°C until used. This sonication procedure has proved satisfactory for preparing active enzyme extracts from the mycoplasmas and lactic acid bacteria used in this study (17,18,24). Immunoloic procedures.…”

“…Various workers (25,31,35,37) have pointed out that physiological and metabolic similarities exist between fermentative mycoplasmas and lactic acid bacteria. When it was observed that Acholeplasma species possess fructose diphosphate-activated lactate dehydrogenases that are strikingly similar to the unique lactate dehydrogenases found in streptococci (21,24,26), a study was initiated to determine whether this large segment of mycoplasmas was phylogenetically related to members of the genus Streptococcus. In this paper we report results of comparative enzyme protein studies which establish that the acholeplasmas are phylogenetically related to 1260 NEIMARK AND LONDON streptococci and that they evolved from streptococci.…”