Techkarnjanaruk Somkiet, Goodman Amanda E
Microbiology (Reading). 1999 Apr;145 ( Pt 4):925-934. doi: 10.1099/13500872-145-4-925.
A cluster of three closely linked chitinase genes organized in the order chiA, chiB and chiC, with the same transcriptional direction, and two unlinked genes, chiP and chiQ, involved in chitin degradation in Pseudoalteromnas sp. strain S91 were cloned, sequenced and characterized. The deduced amino acid sequences revealed that ChiA, ChiB and ChiC exhibited similarities to chitinases belonging to family 18 of the glycosyl hydrolases while ChiP and ChiQ belonged to family 20. ChiP and ChiQ showed different enzymic activities against fluorescent chitin analogues, but neither was able to degrade colloidal chitin. ChiA possessed chitinase activity but did not bind chitin; ChiB bound chitin but had no chitinase activity; ChiC possessed strong chitinase activity and also bound chitin. Production of ChiC in S91 appeared to be controlled by chiA expression, since insertion of a transposon into the ORF of chiA resulted in the loss of chitinase activity as well as loss of ChiC proteins in a chitinase-negative mutant. In Escherichia coli, ChiC appeared to be expressed from its own promoter.
克隆、测序并鉴定了假交替单胞菌属菌株S91中参与几丁质降解的三个紧密连锁的几丁质酶基因簇，其排列顺序为chiA、chiB和chiC，转录方向相同，以及两个不连锁的基因chiP和chiQ。推导的氨基酸序列显示，ChiA、ChiB和ChiC与糖基水解酶家族18的几丁质酶具有相似性，而ChiP和ChiQ属于家族20。ChiP和ChiQ对荧光几丁质类似物表现出不同的酶活性，但均不能降解胶体几丁质。ChiA具有几丁质酶活性，但不结合几丁质；ChiB结合几丁质，但没有几丁质酶活性；ChiC具有很强的几丁质酶活性，并且也结合几丁质。S91中ChiC的产生似乎受chiA表达的控制，因为将转座子插入chiA的开放阅读框会导致几丁质酶阴性突变体中几丁质酶活性丧失以及ChiC蛋白缺失。在大肠杆菌中，ChiC似乎从其自身的启动子表达。
