2 O-TYPE OXIDASES IN METHYLOBACILLUS-FLAGELLATUM-KT

Two oxidases of the o-type in membranes of the methanol-grown obligate methylotroph Methylobacillus flagellatum KT were distinguished. For t his purpose the kinetic analysis of the laser flash-induced optical ab sorbance changes of CO-oxidase complexes under reducing conditions was used. The ratio of these oxidases in membranes greatly depended on th e phases of bacterial growth. One of the oxidases appeared to belong t o the Escherichia coli o-type oxidase family being more sensitive to K CN (K-i = 1 mu M). It showed monophasic CO recombination kinetics with tau 25-30 ms and was expressed in the early exponential phase of grow th. The other oxidase seemed to be similar to the Bacillus sp. FTU o-t ype oxidase being less sensitive to KCN (K-i = 6 mu M), having three-p hasic CO reassociation kinetics with tau 35-70 mu s, 0.25-0.5 ms and 2 -4 ms and dominating in the stationary growth phase. Pyridine haemochr ome spectra showed haems A and D to be absent from the bacterial membr anes. (C) 1994 Academic Press, Inc.