Deranleau D A, Zuber H
Int J Pept Protein Res. 1977;9(4):258-68.
Aminopeptidase I is a membrane-bound metalloenzyme isolated from B. stearothermophilus which is thermostable and requires Co2+ for activity. The Co, Zn, and metal-free enzyme were titrated with ANS, and cooperative binding was noted with the active Co enzyme but not with the Zn (5% active) or apo (inactive) enzymes. There are a number of sites for ANS on each of the three enzyme forms and the agreement between the association constants of the Zn enzyme (identical and independent sites) and the non-cooperative sites of the Co enzyme suggest that these sites are intrinsically similar. However, binding to the first of these sites in the Co enzyme triggers a cooperative binding of a second molecule of ANS, and this cooperative binding is related to a concomitant decrease in enzymatic activity. The correspondence can be shown by comparison of the inhibition constant for the hydrolysis of Gly-Leu-Tyr (Ki-1=13,300 cm3/mmol) and the association constant for the cooperating site (12,500 cm3/mmol). The significance of these observations is discussed in terms of the nature of the binding sites and the possible consequences of the interactions on the regulation of aminopeptidase I activity.
氨肽酶I是一种从嗜热栖热放线菌中分离出的膜结合金属酶，具有热稳定性，且活性需要Co2+。用ANS对含Co、含Zn和不含金属的酶进行滴定，发现活性Co酶存在协同结合，而Zn（5%活性）酶或脱辅基（无活性）酶则没有。三种酶形式各自都有多个ANS结合位点，Zn酶（相同且独立的位点）与Co酶非协同位点的缔合常数之间的一致性表明这些位点本质上相似。然而，与Co酶中这些位点中的第一个位点结合会引发第二个ANS分子的协同结合，这种协同结合与酶活性的相应降低有关。通过比较甘氨酰 - 亮氨酰 - 酪氨酸水解的抑制常数（Ki-1 = 13300 cm3/mmol）和协同位点的缔合常数（12500 cm3/mmol）可以证明这种对应关系。将根据结合位点的性质以及这些相互作用对氨肽酶I活性调节可能产生的后果来讨论这些观察结果的意义。
