Bovine liver rhodanese (thiosulfate : cyanide sulfurtransferase, E.C. 2.8.1.1) was reticulated with bovine serum albumin (BSA) and the resulting rhodanese-BSA copolymers were entrapped in gelatin gels insolubilized with formaldehyde. Coreticulation prevented enzyme release from the gel matrix. Entrapment in the insolubilized gelatin gel allowed the capture of immobilizates having the geometrical configuration of membranes. Activity yields, pH optimum, storage, and thermal stability of both the soluble enzyme-albumin copolymers (SIE) and the gel-entrapped enzyme (GEE) were investigated and compared with those of free enzyme. Entrapment significantly affected activity yields due to partial denaturation during immobilization whereas enzyme stability was enhanced. GEE completely retained initial activity after 30 days of storage at 4 degrees C or a 30 min incubation at 52 degrees C. Hysteretic behavior of SIE was noted. Further, inactivation during the catalytic cycle of free enzyme and the two immobilized species was investigated and attributed to oxidation phenomena as demonstrated by the possibility of regenerating GEE with a reducing agent (sodium salt of the thioglycolic acid, TGA). TGA also enhanced storage stability of the three enzymatic preparations. The behavior of GEE in a plug-flow reactor (PER) was examined and compared to that obtained in a continuously stirred tank reactor (CSTR).