[Alternativity of methane assimilation pathways in obligate methylotrophs]

The activity of key enzymes involved in the primary pathways of methane assimilation and enzymes of the citrate cycle was determined in various obligate methylotrophs: mesophilic, thermotolerant, and thermophilic. The bacteria are characterized by the membrane ultrastructure of the I type, high activity of hexosephosphate synthase, NAD- and NADP-specific isocitrate dehydrogenase, and the absence of alpha-ketoglutarate dehydrogenase. The bacteria also displayed the activity of key enzymes of the serine cycle, hydroxypyruvate reductase, and serineglyoxylate aminotransferase. Therefore, both the ribulose monophosphate and serine pathways are involved in methane assimilation, and the division of methanotrophs into two groups, according to their metabolism, is tentative.