Polymerization of Several Proteins by Ca²⁺-Independent Transglutaminase Derived from Microorganisms

Abstract

α_s1-Casein and soybean globulins were polymerized and gelatinized by Ca₂₊-independent transglutaminase that was isolated from the culture filtrate of a microorganism thought to belong to Streptoverticillium sp. of actinomycetes. This enzyme polymerized such albumins as bovine serum albumin, human serum albumin and conalbumin in the presence of dithiothreitol. Rabbit myosin was polymerized by the present emzyme but actin was not. An RP-HPLC analysis after enzymic digestion of the polymerized α_s1-casein showed existence of the ε-(γ-Glu)Lys bond. Thus, it was confirmed that the polymerization was formed by a catalytic reaction of the transglutaminase.