酵母細胞壁溶解酵素による酵母の消化

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Digestibility of heart-treated yeast cells with pepsin was shown to be extremely low due to the existence of barrier (cell wall) to the penetration of the enzyme, as evidenced by the experiment depicted in Fig. 1; very high degestibililty was observed with disrupted cells.Slight hydrolysis of yeast cell wall with the yeast cell wall-lytic enzyme of Streptomyces albidoflavus resulted in a remarkable increase in pepsin digestibility (Fig 3).In this case, heart-treated cells were subjected to the action of the lytic enzyme to a so slight extent that no morphological change of cells could be detected microscopically.As intact yeast cells were much more resistant to the lytic enzyme than heat-treated one, the pretreatment with so small amount of the lytic enzyme as above produced no remarkable effect on pepsin digestibility in the case of intact cells (Fig. 2).The protease fraction in the lytic enzyme preparation had the activity optimum in alkaline region, as reported previously. Therefore, a high value of pepsin digestibility obtained by lytic enzyme-pretreatment at pH 6 (Fig. 4) indicated that β-1,3-glucanase was mainly responsible for the above mentioned effect. The protease in the lytic enzyme system could produce amino acids from heat-treated yeast cell in a good yield when much more of the enzyme preparation was used (Fig.5; 6); the digestion rate was highest at 60℃ as well as at 50℃, owing to the protection by the substrate from heat inactivation (Fig. 7). In this case, cell concentration in a reaction mixture could be increased to 17% without appreciale degrease in degestion rate (Fig. 8). Addition of "Pronase", Bacillus subtilis protease or thermophilic protease of bacterial origin (each 500 PU per g of yeast cell) to the reaction mixture containing the same activity of the lytic enzyme did not cause accelerated digestion (Fig.9).The lytic cenzyme was shown to be highly effective in promoting solubilization of RNA in heat-in heat-treated yeast cells (Fig.10).The yeast cell wall-lytic enzyme showed relatively broad spectrum of action, besides most of yeast and molds tested, Gram-negative bacteria could be lysed (Table 1).
社団法人日本生物工学会の論文
1965-10-25

酵母細胞壁溶解酵素による酵母の消化

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