Kruus K, Andreacchi A, Wang W K, Wu J H
University of Rochester, Department of Chemical Engineering, NY 14627-0166, USA.
Appl Microbiol Biotechnol. 1995 Dec;44(3-4):399-404. doi: 10.1007/BF00169935.
CelS is the most abundant subunit and an exoglucanase component of the Clostridium thermocellum cellulosome, multicomponent cellulase complex. The product inhibition pattern of CelS was examined using purified recombinant CelS (rCelS) produced in Escherichia coli. The rCelS activity on cellopentaose was strongly inhibited by cellobiose. The rCelS activity was also inhibited by lactose. Glucose was only marginally inhibitory. Cellobiose appeared to inhibit the rCelS activity through a competitive mechanism. The inhibition was relieved when beta-glucosidase was added, presumably because of the conversion of cellobiose into glucose. These hydrolysis product inhibition patterns are consistent with those of the crude enzyme (cellulosome), suggesting that CelS is a rate-limiting factor in the activity of the cellulosome.
CelS是嗜热栖热梭菌纤维小体（多组分纤维素酶复合物）中含量最丰富的亚基和一种外切葡聚糖酶成分。使用在大肠杆菌中产生的纯化重组CelS（rCelS）检测了CelS的产物抑制模式。纤维二糖强烈抑制rCelS对纤维五糖的活性。乳糖也抑制rCelS的活性。葡萄糖的抑制作用很微弱。纤维二糖似乎通过竞争机制抑制rCelS的活性。添加β-葡萄糖苷酶后抑制作用解除，推测这是由于纤维二糖转化为葡萄糖所致。这些水解产物抑制模式与粗酶（纤维小体）的模式一致，表明CelS是纤维小体活性的限速因子。
