Multiple genes involved in chitin degradation from the marine bacterium Pseudoalteromonas

School of Biological Sciences, The Flinders University of South Australia, GPO Box 2100, Adelaide, SA 5001, Australia 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, Chis 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; Chis bound chitin but had no chitinase activity; Chic possessed strong chitinase activity and also bound chitin. Production of Chic in 591 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 chitinasenegative mutant. In Escherichia coli, Chic appeared to be expressed from its own promoter.