Protection and enhancement of ribulose 1,5 bisphosphate carboxylase activity by exogenous proteins

Abstract

When assayed in vitro, the activity of the photosynthetic enzyme ribulose 1,5 bisphosphate carboxylase oxygenase is both enhanced and protected from spontaneous decay by exogenous proteins such as hemoglobin, serum albumin, and aldolase. Other proteins and amino acids tested are either ineffective (lysozyme, ferritin, lysine, and cysteine) or afford only partial protection (catalase, glycine, and phenylalanine). Protective proteins do not bind to, or exchange disulfides with, ribulose 1.5 bisphosphate carboxylase/oxygenase. Since their effect can be mimicked by reductively treated detergents such as Triton X-100, it appears that proteins protect from decay by quenching the spontaneous oxidative degradation and inhibiting surface adsorption which could lead to enzyme unfolding. Release of adsorbed molecules from the container surface is likely to be the cause of carboxylase activity enhancement.

REDOX PROPERTIES ARE CONSERVED IN RUBISCOS FROM DIATOMS AND GREEN ALGAE THROUGH A DIFFERENT PATTERN OF CYSTEINES1

“…1, black bars). This result suggests a higher sensitivity of RUBISCO from diatoms to oxidation (which might result from mild oxidizing conditions along the purification process), when compared to RUBISCO from C. reinhardtii and other green‐like RUBISCOs (Peñarrubia and Moreno 1991, Garcia‐Ferris and Moreno 1993).…”