Rabinovich M L, Nguen V V, Klesov A A
Biokhimiia. 1982 Mar;47(3):465-77.
The affinity of cellulolytic enzymes of various origin for microcrystalline cellulose (MCC) in a column type reactor has been studied. It was shown that there exist two types of the enzymes differing in their ability to bind to cellulose and to degrade MCC. One group of cellulases is characterized by weak affinity for MCC and by a rather low degree of conversion of this substrate into soluble products, but shows a burst of soluble products during the initial period of the hydrolysis. On the contrary, the other group of the enzymes irreversibly binds to cellulose and shows a noticeable ability to solubilize MCC. The results obtained suggest that the weak binding reflects a productive enzyme--cellulose interaction by the enzyme active center, like its interaction with soluble polymeric substrates. The tight binding, on the other hand, is less productive and reflects the interaction of peripheral parts of the enzymes with the cellulose surface. The hydrolytic action of the tightly adsorbed cellulases proceeds on the substrate surface consecutively, without leaving the insoluble substrate between the catalytic acts and the enzymes might steadily penetrate into the cellulose matrix. This in turn might induce mechanical fragmentation of the substrate. The rate of action of adsorbed cellulases can be limited by their diffusion along the surface or into the cellulose matrix. A decrease of the ionic strength weakens the cellulase affinity for cellulose, which in its turn leads to an increase in the initial burst of the soluble products of cellulose hydrolysis and a respective decrease of efficiency of cellulose conversion into glucose. It is concluded that the principal factor which determines the ability of cellulases to degrade crystalline cellulose is the affinity (i. e. degree of adsorption) of the enzymes for the insoluble substrate.
研究了不同来源的纤维素分解酶在柱式反应器中对微晶纤维素（MCC）的亲和力。结果表明，存在两种类型的酶，它们在与纤维素结合及降解MCC的能力方面有所不同。一类纤维素酶的特点是对MCC的亲和力较弱，该底物转化为可溶性产物的程度较低，但在水解初期会出现可溶性产物的爆发。相反，另一类酶与纤维素不可逆结合，并表现出明显的溶解MCC的能力。所得结果表明，弱结合反映了酶活性中心与纤维素之间有效的酶 - 纤维素相互作用，就像它与可溶性聚合物底物的相互作用一样。另一方面，紧密结合的效率较低，反映了酶的外围部分与纤维素表面的相互作用。紧密吸附的纤维素酶的水解作用在底物表面连续进行，催化作用之间不会留下不溶性底物，并且酶可能会稳定地渗透到纤维素基质中。这反过来可能会导致底物的机械破碎。吸附的纤维素酶的作用速率可能受其沿表面或进入纤维素基质的扩散限制。离子强度的降低会削弱纤维素酶对纤维素的亲和力，这进而导致纤维素水解可溶性产物的初始爆发增加，以及纤维素转化为葡萄糖的效率相应降低。得出的结论是，决定纤维素酶降解结晶纤维素能力的主要因素是酶对不溶性底物的亲和力（即吸附程度）。
