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Properties of Malic Enzyme from the Aerobic Methanotroph Methylosinus trichosporium

O. N. Rozova1, V. N. Khmelenina1,a*, I. I. Mustakhimov1, S. Y. But1, and Yu. A. Trotsenko1

1G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Federal Research Center “Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences”, 142290 Pushchino, Moscow Region, Russia

* To whom correspondence should be addressed.

Received August 14, 2018; Revised December 12, 2018; Accepted December 12, 2018
Recombinant malic enzyme from the aerobic methanotroph Methylosinus trichosporium was obtained by heterologous expression in Escherichia coli and purified by affinity metal-chelating chromatography. The homohexameric enzyme of 6×80 kDa catalyzed the reversible reaction of oxidative decarboxylation of malate to pyruvate in the presence of mono- and divalent cations and NADP+ as a cofactor. The kcat/Km ratio indicated much higher catalytic efficiency of the malate decarboxylation reaction as compared with the pyruvate carboxylation reaction. Analysis of the protein sequence revealed that the C-region of the enzyme contains a large domain homologous to phosphoacetyltransferase, but no phosphoacetyltransferase activity was detected either for a full chimeric malic enzyme or for the C-end fragment obtained as a separate protein. This C-end domain promoted activity of the malic enzyme.
KEY WORDS: malic enzyme, methanotrophs, Methylosinus trichosporium

DOI: 10.1134/S0006297919040060