Multiple genes involved in chitin degradation from the marine bacterium Pseudoalteromonas sp. strain S91

A cluster of three closely linked chitinase genes organized in the order ch iA, chiB and chiC, with the same transcriptional direction, and two unlinke d genes, chiP and chiB involved in chitin degradation in Pseudoalteromnas s p. strain S91 were cloned, sequenced and characterized. The deduced amino a cid sequences revealed that ChiA, ChiB and ChiC exhibited similarities to c hitinases belonging to family 18 of the glycosyl hydrolases while ChiP and ChiQ belonged to family 20. ChiP and ChiQ showed different enzymic activiti es against fluorescent chitin analogues, but neither was able to degrade co lloidal chitin. ChiA possessed chitinase activity but did not bind chitin; ChiB bound chitin but had no chitinase activity; ChiC possessed strong chit inase 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 app eared to be expressed from its own promoter.