Presence of Anaplerotic Reactions and Transamination, and the Absence of the Tricarboxylic Acid Cycle in Mollicutes

Abstract

Cell extracts of the fermentative Mollicutes Acholeplasma laidlawii B-PG9, Acholeplasma morum S2, Mycoplasma capricolum 14, Mycoplasma gallisepticum S6, Mycoplasma pneumoniae FH, Mycoplasma hyopneumoniae J and M. genitalium G-37, and the non-fermentative Mycoplasma hominis PG-21, Mycoplasma hominis 1620 and Mycoplasma bovigenitalium PG-11 were examined for 39 cytoplasmic enzyme activities associated with the tricarboxylic acid (TCA) cycle, transamination, anaplerotic reactions and other enzyme activities at the pyruvate locus. Malate dehydrogenase (EC 4.2.1.2) was the only TCA-cycle-associated enzyme activity detected and it was found only in the eight Mycoplasma species. Aspartate aminotransferase (EC 2.6.1.1) activity was detected in all Mollicutes tested except M. gallisepticum S6. Malate synthetase (EC 4.1.3.2) activity, in the direction of malate formation, was found in the eight Mycoplasma species, but not in any of the Acholeplasma species. Phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) was detected in the direction of oxaloacetate (OAA) formation in both Acholeplasma species, but not in any of the Mycoplasma species. Pyruvate carboxylase (EC 6.4.1.1), pyruvate kinase (EC 2.7.1.40), pyruvate dehydrogenase (EC 1.2.4.1) and lactate dehydrogenase (EC 1.1.1.27) activities were found in all ten Mollicutes tested. No activities were detected in any of the ten Mollicutes for aspartase (EC 4.3.1.1), malic enzyme (EC 1.1.1.40), PEP carboxytransphosphorylase (EC 4.1.1.38), PEP carboxykinase (EC 4.1.1.32) or pyruvate orthophosphate dikinase (EC 2.7.9.1). In these TCA-cycle-deficient Mollicutes the pyruvate-OAA locus may be a point of linkage for the carbons of glycolysis, lipid synthesis, nucleic acid synthesis and certain amino acids. CO2 fixation appears obligatory in the Acholeplasma species and either CO2 fixation or malate synthesis appears obligatory in the Mycoplasma species.

DNA sequence determination and biochemical analysis of the immunogenic protein P36, the lactate dehydrogenase (LDH) of Mycoplasma hyopneumoniae

“…hyopneumoniae LDH activity seems to be common to mycoplasmas including M . hyopneumoniae (Manolukas et al, 1988) which produces in culture conditions a LDH activity of 217f2 U (mgprotein)-'. At first glance, it seems surprising that M. hyopneumoniae LDH is an early and strongly immunogenic protein in naturally or experimentally infected pigs.…”

Differential Inhibition of Mollicute Growth: an Approach to Development of Selective Media for Specific Mollicutes

“…PDHC has been reported in all Acholeplasma and Mycoplasma species studied, including M. verecundum (3,7). Nevertheless, it appeared to be possible that the role of PDHC might be greater in organic acid-oxidizing species, especially those that appear to be dependent solely on the oxidation of pyruvate for ATP synthesis.…”

Identification and analysis of the genes coding for the putative pyruvate dehydrogenase enzyme complex in Acholeplasma laidlawii

“…The PDH enzyme activity detected in A. laidlawii (42,45) is, at least partially, associated with the membrane fraction (13,67). In accordance, the putative PDH-E2 subenzyme is detected in the membrane fraction by immunoblotting (Fig.…”

“…3). It should be emphasized that A. laidlawii has no OGDH (13,42). In addition to the 75-kDa protein, a 34-kDa protein was also expressed from pB15 and the pUC derivative (see above) as observed with SDS-PAGE (64).…”

“…laidlawii ferments glucose to lactate, pyruvate, and acetate but lacks the tricarboxylic acid cycle and cytochromes (42,52). Saturated but not unsaturated fatty acids can be synthesized from acetyl coenzyme A byA.…”