Purification and characterization of alkaline proteinase front Atlantic menhaden muscle

Two alkaline proteinases (A and B) were isolated and found to be composed of homogeneous subunits. These proteinases, A and B, were concentrated 62.9- and 986.5-fold compared to the crude muscle extract, with molecular weights of 707,000 and 450,000, respectively. Both are probably serine type proteinases, and optimum caseinolytic activity was shown at pH 8.0 and 55 degrees C. Both degraded actomyosin under similar conditions. Enzyme A had higher thermal stability than B. The residual activities of A and B in 3.6% NaCl solution were 95% and 85%. These data suggest that these proteinases are involved in the softening of menhaden surimi gels which occurs during heating at 50 to 70 degrees C.