The Enzymic Activity of the Outer Shell of Lactobacillus arabinosus

Abstract

Preparations of the outer shell of L. arabinosus were made by crushing the bacteria in a Hughes press and removing the cytoplasm by washing and centrifugation. Such preparations had none of the enzymes associated with flavin-mediated oxidation; they consistently had adenosine triphosphatase (ATPase) activity. The kinetics and other properties of this enzyme were studied. The evidence suggested that the enzyme was bound to the cytoplasmic membrane, the bulk of which appeared to be within the cell wall. The preparation was thus similar to that from obligate facultative aerobes and which, in contrast to the preparations from lactobacilli, contained enzymes associated with oxygen utilization mediated by the cytochrome hydrogen-transport system. The bound ATPase had an optimum at pH 6.0 and was not markedly inhibited by ouabain or oligomycin: it was stimulated by 2,4-dinitrophenol. It was thus different from ATPase associated with ion transport but similar to that from mitochondrial membranes. There was no nucleotide pyrophosphorylase activity in the preparation but other nucleotide triphosphates and diphosphates and some inorganic phosphates were hydrolyzed but at slower rates than was ATP.