Oligomeric forms of bacterial malate dehydrogenase: a study of the enzyme from the phototrophic non-sulfur bacterium Rhodovulum steppense A-20s

Abstract

Malate dehydrogenase (EC 1.1.1.37) was purified to homogeneity from the phototrophic purple non-sulfur bacterium Rhodovulum steppense A-20s. According to gel-chromatography and electrophoretic studies, malate dehydrogenase is present as a dimer, tetramer and octamer depending on cultivation conditions. In phototrophic aerobic conditions only the tetrameric form was present, in chemotrophic aerobic conditions all three forms were detected, while in the absence of oxygen the octameric form disappeared. The malate dehydrogenase oligomers are encoded by a single gene and composed of the same 35 kDa polypeptide but differ in pH and temperature optimum, in affinities to malate, oxaloacetate, NADH and NAD and in regulation by cations and citrate. By modulating the cultivation conditions, it has been established that the dimer participates in the glyoxylate cycle; the tetramer operates in the tricarboxylic acid cycle, and the octamer may be involved in the adaptation to oxidative stress.

Nitrogen Fixation Activity and Genome Analysis of a Moderately Haloalkaliphilic Anoxygenic Phototrophic Bacterium Rhodovulum tesquicola

“…The methylaspartate and glyoxylate pathways are incomplete. Although there is evidence for the isocitrate lyase presence in R. steppense [44], we have found no corresponding or homologous genes in any of the three genomes studied. Thus, the detection of the potential presence and functioning of glyoxylate cycle is a subject of further research.…”

Engineered Mutants of a Marine Photosynthetic Purple Nonsulfur Bacterium with Increased Volumetric Productivity of Polyhydroxyalkanoate Bioplastics

“…Thus, a better oxidation–reduction (redox) status regulation ability could be the main reason for the rapid growth phenotype in the presence of malate and/or pyruvate. One possible factor regulating the redox status is the presence of three oligomeric forms (dimer, tetramer, and octamer) of malate dehydrogenase in Rhodovulum species; these forms are involved in rapid equilibration of the NADH/NAD + and malate/oxaloacetate ratios according to cultivation conditions . However, it is unclear at this point how redox regulation works differently in the mutants, which still requires further investigation.…”

Screening of Potential Key Transcripts Involved in Planarian Regeneration and Analysis of Its Regeneration Patterns by PacBio Long-Read Sequencing

“…Among the predicted proteins of selected transcripts, MDH1 participates in the citrate cycle, catalyzing the dehydrogenation of L-malic acid and interconversion with oxaloacetate (Eprintsev et al, 2018). ACLY, which catalyzes the formation of acetyl-CoA and oxaloacetate from citrate and CoA, is a positive regulator in glycolysis (Watson et al, 1969).…”