title: Chitinase in bean leaves: induction by ethylene, purification, properties, and possible function.
abstract: Ethylene induced an endochitinase in primary leaves of Phaseolus vulgaris L. The enzyme formed chitobiose and higher chitin oligosaccharides from insoluble, colloidal or regenerated chitin. Less than 5% of the total chitinolytic activity was detected in an exochitinase assay proposed by Abeles et al. (1970, Plant Physiol. 47, 129-134) for ethylene-induced chitinase. In ethylene-treated plants, chitinase activity started to increase after a lag of 6 h and was induced 30 fold within 24 h. Exogenously supplied ethylene at 1 nl ml(-1) was sufficient for half-maximal induction, and enhancement of the endogenous ethylene formation also enhanced chitinase activity. Cycloheximide prevented the induction. Among various hydrolases tested, only chitinase and, to a lesser extent, β-1,3-glucanase were induced by ethylene. Induction of chitinase by ethylene occurred in many different plant species. Ethylene-induced chitinase was purified by affinity chromatography on a column of regenerated chitin. Its apparent molecular weight obtained by sodium dodecyl sulfate-gel electrophoresis was 30,000; the molecular weight determined from filtration through Sephadex G-75 was 22,000. The purified enzyme attacked chitin in isolated cell walls of Fusarium solani. It also acted as a lysozyme when incubated with Micrococcus lysodeikticus. It is concluded that ethylene-induced chitinase functions as a defense enzyme against fungal and bacterial invaders.
authors.affiliation: Botanisches Institut der Universität, Schönbeinstrasse 6, CH-4056, Basel, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Boller
authors.forename: A
authors.initials: A
authors.lastname: Gehri
authors.forename: F
authors.initials: F
authors.lastname: Mauch
authors.forename: U
authors.initials: U
authors.lastname: Vögeli