Abstract
Mushrooms have occasionally been used for cooking pot-steamed hotchpotch (tyawanmushi), but solidification has not been possible following the addition of Grifola frondosa. Therefore, proteinases in Grifola frondosa may degrade egg white protein. Ovalbumin (OVA) was digested with an extract of G. frondosa at acid, neutral or slightly alkaline pH, judging from SDS-PAGE patterns. After DEAE-cellulose column chromatography and gel filtration on Sephadex G-75, three proteinases and an acid proteinase from G. frondosa were identified. The molecular weight of proteinase A was about 18, 000 and its enzymatic properties were essentially the same as those of alkaline metal proteinase, reported by Hashimoto et al. However, proteinase B appeared to be a new proteinase because of its high molecular weight of about 44, 000, and neutral optimum pH. Proteinase C was present in the smallest amount and could only be poorly characterized. Acid proteinase was a carboxyl proteinase inhibited by pepstatin. Each proteinase digested OVA, but the SDS-PAGE patterns of the digestion products indicated hydrolytic specificity towards OVA. No proteinase alone could prevent OVA and egg white gelling, but a mixture of the three proteinases prevented gelling. Proteinases present in G. frondosa would thus appear to degrade egg white protein and prevent its gelling.
