CHANGES IN THE ACTIVITY OF 2 HISTIDINE DECARBOXYLASES FROM PHOTOBACTERIUM-PHOSPHOREUM DURING GROWTH UNDER DIFFERENT OXYGEN-TENSIONS

Changes in the activity of two histidine decarboxylases from Photobacterium phosphoreum during the growth of different oxygen tensions and some properties of the enzymes were studied. The specific activity of the enzyme of crude extract was highest in the anaerobic stationary culture and higher in the aerobic stationary culture than in the aerobic shaking culture, in contrast with growth. The pattern of variation of the specific activity during growth differed between the anaerobic and aerobic stationary cultures and the aerobic shaking culture. The enzyme was composed of at least two enzymes with molecular weights of about 700,000 (peak I) and 107,000 (peak II). Peak I was considered as constitutive enzyme and peak II as inducible enzyme. The enzyme of peak I was labile but that of peak II was stable in the presence-of dithiothreitol (DTT). The activities of peaks I and II varied with different oxygen tensions of the culture; the percent activity increased in peak I but decreased in peak II with increasing oxygen tension. Therefore, it has been suggested that the histamine-forming ability is affected by the quality as well as the quantity of enzyme.