The photosensitivity of the malate oxidase system of a pigmented strain and a carotenoidless mutant of Sarcina lutea (Micrococcus luteus).

The effect of white light on the malate oxidase of Sarcina lutea (Micrococcus luteus) membranes has been examined using a carotenoid-containing and a carotenoidless mutant. At least three photosensitive sites have been detected. Two of these are associated with the malate dehydrogenase complex (malate-menaquinone reductase) and are unaffected by membrane carotenoid. A third site which has been detected beyond the dehydrogenase complex, is protected by carotenoid since it can only be demonstrated in carotenoidless systems. A repair mechanism has been found for one of the two sites in the dehydrogenase complex.