STRUCTURAL AND FUNCTIONAL-CHARACTERISTICS OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE FROM SPIRULINA-PLATENSIS

Optimization of protein extraction for food use by wet fractionation p rocedure requires knowledge of the possible degradation processes whic h usually accompany the purification procedures mid of the basic molec ular features of the particular protein. Proteolytic degradation of ri bulose-1,5-bisphosphate carboxylase (RuBPcase) observed in crude extra cts of Spirulina platensis was partially inhibited by the addition of phenyl-methyl-sulphonyl-fluoride as a proteinase inhibitor. The RuBPca se purified to electrophoretic homogeneity by a laboratory method was characterized for molecular weight, isoelectric point, solubility as a function of pH and ionic strength, and heat stability. Since degradat ion of purified plant RuBPcase is related to the redox state of enzyme thiol groups we have investigated the relationship between the number of oxidized thiol groups and the residual activity in the purified pr eparation of RuBPcase from Spirulina platensis. Furthermore, the susce ptibility of the enzyme to various transition metals, able to catalyse the oxidation of thiol groups, was evaluated and the functional role of thiol groups for the maintenance of the native structure of RuBPcas e is discussed. The results obtained are presented and discussed in vi ew of the potential industrial extraction of RuBPcase from Spirulina p latensis. (C) 1997 Academic Press Limited.