Cloning of the Malic Enzyme Gene from Corynebacterium glutamicum and Role of the Enzyme in Lactate Metabolism

Abstract

Malic enzyme is one of at least five enzymes, known to be present in Corynebacterium glutamicum, capable of carboxylation and decarboxylation reactions coupling glycolysis and the tricarboxylic acid cycle. To date, no information is available concerning the physiological role of the malic enzyme in this bacterium. The malE gene from C. glutamicum has been cloned and sequenced. The protein encoded by this gene has been purified to homogeneity, and the biochemical properties have been established. Biochemical characteristics indicate a decarboxylation role linked to NADPH generation. Strains of C. glutamicum in which the malE gene had been disrupted or overexpressed showed no detectable phenotype during growth on either acetate or glucose, but showed a significant modification of growth behavior during lactate metabolism. The wild type showed a characteristic brief period of exponential growth on lactate followed by a linear growth period. This growth pattern was further accentuated in a malE-disrupted strain (⌬malE). However, the strain overexpressing malE maintained exponential growth until all lactate had been consumed. This strain accumulated significantly larger amounts of pyruvate in the medium than the other strains.

Expression of the Escherichia coli pntAB genes encoding a membrane-bound transhydrogenase in Corynebacterium glutamicum improves l-lysine formation

“…Both pathways require 4 mol NADPH per mol lysine starting from oxaloacetate. In principle, NADPH can be synthesized in C. glutamicum by the enzymes of the oxidative pentose phosphate pathway (PPP), glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase (Moritz et al 2000), by isocitrate dehydrogenase (Eikmanns et al 1995) and by malic enzyme (Gourdon et al 2000). Carbon flux analysis revealed that during growth on glucose, NADPH for lysine biosynthesis is provided by the PPP, whereas isocitrate dehydrogenase and malic enzyme are of minor importance (Marx et al 1996(Marx et al , 1997(Marx et al , 1999.…”

Characterization of an oxaloacetate decarboxylase that belongs to the malic enzyme family

“…In fact, we determined that dinucleotides inhibited the reaction. When either 0.50 mM NAD þ or 0.50 mM NADH was added, the specific activity was reduced by approximately 50% ( [6]. However, no signal could be detected.…”

“…The prokaryotic MEs described so far are fewer in number and more diverse in structure than their eukaryotic counterparts. MEs have been characterized from Bacillus stearothermophilus [2], Sulfolobus solfataricus [3], Rhizobium meliloti [4,5], Corynebacterium glutamicum [6] and Streptococcus bovis [7].…”

Analysis and Engineering of Metabolic Pathway Fluxes in Corynebacterium glutamicum

“…For malic enzyme no clear effects could be observed so far. Neither deletion nor overexpression of the corresponding gene influenced the metabolism of C. glutamicum on sugars markedly [21,152].…”

“…For anaplerotic replenishment of the TCA cycle, C. glutamicum exhibits pyruvate carboxylase [20] and phosphoenolpyruvate (PEP) carboxylase as carboxylating enzymes. Malic enzyme [21] and PEP carboxykinase [22,23] catalyze decarboxylation reactions from the TCA cycle towards glycolysis. As additional gluconeogenetic enzymes, oxaloacetate decarboxylase [24] and PEP synthetase [25] have been proposed.…”