A photoinduced H-2 production system, coupling D-maltose degradation by glucoamylase and glucose dehydrogenase (GDH) and H-2 production with colloidal platinum as a catalyst using the visible light-induced photosensitization of Mg chlorophyll-a (Mg Chl-a), has been developed. H-2 production was continuous when the reaction mixture containing D-maltose, glucoamylase, GDH, NAD(+), MgChl-a, Methyl Viologen (MV2+, an electron relay reagent) and colloidal platinum was irradiated by visible light. The amount of H-2 production was estimated to be 5 +/-0.5 mumol after 4 h irradiation. The yield of the conversion of D-maltose to H-2 in this system was ca. 1.8%.