Preparation of soluble-insoluble interconvertible enzymes: Enzymepolymerized .ALPHA.S1-casein conjugates.

Abstract

α_s1-Casein can be made either soluble or insoluble by adjusting the concentration of coexisting calcium ions. In this study, we tried to make a soluble-insoluble interconvertible enzyme through the formation of a conjugate of an enzyme and α_s1-casein using a heterobifunctional crosslinking reagent, N-succinimidyl 3-(2-pyridyldithio)propionate. The conjugate of phosphoglyceromutase and native α_s1-casein did not exhibit sufficient calcium-dependent precipitation. However, conjugates of enzymes (phosphoglyceromutase, enolase or peroxidase) and α_s1-casein polymerized by transglutaminase precipitated almost completely in the presence of more than 50mM CaCl₂. Most of the enzyme conjugates precipitated as calcium casemates could be solubilized reversibly with EDTA, without a significant loss of activity. A mixture of the enzymea-polymerized α_s1-casein conjugates prepared with phosphoglyceromutase, enolase and pyruvate kinase could catalyze sequential reactions which convert D-3-phosphoglycerate into pyruvate with the same efficiency as a mixture of free enzymes. These results indicate that conjugates of enzymes and polymerized α_s1-casein can be useful as soluble-insoluble interconvertible enzymes.