PHOTOSENSITIVE PHENOMENA OF NITRILE HYDRATASE OF Rhodococcus sp. N‐771

When the washed cells of Rhodococcus sp. N‐771 were incubated at 5°C in the dark under aerobic condition, their nitrile hydratase was inactivated after several days. Most of this activity was recovered by light irradiation. The speed of inactivation in the dark was affected by incubation temperature and amount of oxygen supply. Under anerobic conditions, however, this reversible dark inactivation was not observed; the photoirradiation of the cells irreversibly inactivated the initial cell activity by about 15%. The enzyme activity of the cell‐free extract of the inactivated cells can also be recovered when photoirradiated. This process did not require oxygen, and was not prevented by dialysis. However, the enzyme of the cell‐free extract could not be inactivated by dark, aerobic incubation nor by photoirradiation after dark anaerobic incubation.