Bromelain, papain, and ficin are studied the most for meat tenderization, but have limited application due to their short lifetime. The aim of this work is to identify the adsorption mechanisms of these cysteine proteases on chitosan to improve the enzymes' stability. It is known that immobilization can lead to a significant loss of enzyme activity, which we observed during the sorption of bromelain (protease activity compared to soluble enzyme is 49% for medium and 64% for high molecular weight chitosan), papain (34 and 28% respectively) and ficin (69 and 70% respectively). Immobilization on the chitosan matrix leads to a partial destruction of protein helical structure (from 5 to 19%). Using computer modelling, we have shown that the sorption of cysteine proteases on chitosan is carried out by molecule regions located on the border of domains L and R, including active cites of the enzymes, which explains the decrease in their catalytic activity upon immobilization. The immobilization on chitosan does not shift the optimal range of pH (7.5) and temperature values (60 °C for bromelain and papain, 37–60 °C for ficin), but significantly increases the stability of biocatalysts (from 5.8 times for bromelain to 7.6 times for papain).

菠萝蛋白酶，木瓜蛋白酶和丝蛋白对肉嫩化的研究最多，但由于寿命短而限制了其应用。这项工作的目的是确定这些半胱氨酸蛋白酶在壳聚糖上的吸附机理，以提高酶的稳定性。众所周知，固定化会导致酶活性的显着降低，我们在菠萝蛋白酶的吸附过程中观察到（与可溶性酶相比，蛋白酶活性，中等分子量为49％，高分子量壳聚糖为64％），木瓜蛋白酶（34和28分别为％和Ficin（分别为69％和70％）。固定在壳聚糖基质上会导致蛋白质螺旋结构的部分破坏（5％至19％）。使用计算机建模，我们已经表明，半胱氨酸蛋白酶在壳聚糖上的吸附是通过位于结构域L和R的边界上的分子区域进行的，包括酶的活性部位，这解释了固定化后它们催化活性的降低。固定在壳聚糖上不会改变pH的最佳范围（7.5）和温度值（菠萝蛋白酶和木瓜蛋白酶为60°C，丝蛋白为37–60°C），但是会显着提高生物催化剂的稳定性（从菠萝蛋白酶的5.8倍增加到菠萝蛋白酶的5.8倍）。木瓜蛋白酶的7.6倍）。