SUMMARY: Chitinases were isolated from the grains of wheat, barley and maize, and compared with those obtained from Serratia marcescens, Streptomyces griseus and Pseudomonas stutzeri for antifungal activity and enzyme specificity. The six enzymes were tested for antifungal activity using an assay based upon inhibition of hyphal extension of the fungi Trichoderma reesei and Phycomyces blakesleeanus. Antifungal activity was observed with as little as 1 μg of each of the grain chitinases, whereas none of the bacterial chitinases had any effect on hyphal extension, even at 50 μg chitinase per assay. This difference in antifungal activity correlated with the different mechanisms of action of the two classes of enzymes. In common with other plant chitinases, the grain chitinases functioned as endochitinases and contained lysozyme activity. In contrast, the bacterial enzymes were exochitinases and hydrolysed the chromogenic trisaccharide analogue p-nitrophenyl-β-D-N, N'-diacetylchitobiose, which proved to be an excellent substrate for assaying bacterial chitinases. These experiments strengthen the hypothesis that plant chitinases function to protect the host against fungal infections.

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Plant and bacterial chitinases differ in antifungal activity

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.

Chitinase in bean leaves: induction by ethylene, purification, properties, and possible function

Publisher Summary In their carbohydrate metabolism, insects make use of substances, enzymes and operational principles that are known from other living groups. Occupying a central place among the knowledge of carbohydrate metabolism in insects is the presence of trehalose as the predominant blood sugar. Its distribution and the relations of its metabolism to the mechanisms of nutrient absorption, storage and supply to the tissues, are discussed. Characteristic of insects and other arthropods is the presence of chitin as a structural component of the exoskeleton, which in its deposition and resorption interacts closely with the metabolism of other carbohydrates. The mucopolysaccharides of insect hemolymph and tissues have only recently begun to be investigated. This chapter focuses on a metabolic process, which apparently peculiar to insects and some other arthropods is the bulk conversion of glycogen to glycerol and sorbitol. Insects have provided the material for several well-known original biochemical discoveries. The chapter also presents an investigation of the biochemistry of this animal group, which has in general lagged far behind that of micro-organisms on the one hand and vertebrate animals on the other.

The Biochemistry of Sugars and Polysaccharides in Insects

7 – Biochemistry of Digestion

Certain fly larvae can infest corpses or the wounds of live hosts. Those which are least invasive on live hosts have been used therapeutically, to remove dead tissue from wounds, and promote healing. This medicinal use of maggots is increasing around the world, due to its efficacy, safety and simplicity. Given our low cultural esteem for maggots, the increasing use and popularity of maggot therapy is evidence of its utility. Maggot therapy has successfully treated many types of chronic wounds, but much clinical and basic research is needed still. In this review, the biology of myiasis and the history of maggot therapy are presented, the current status of our understanding and clinical use of medicinal maggots is discussed, and opportunities for future research and applications are proposed.

Medicinal Maggots: An Ancient Remedy for Some Contemporary Afflictions

Studies on the chitinase system in bean and other seeds.

Separation of chitin oligosaccharides by thin-layer chromatography.

Detection of chitin oligosaccharides on paper chromatograms

An examination of proteolytic enzymes from several insects for collagenase activity

Studies on the digestive proteinase of clothes moth larvae (Tineola bisselliella)—II: Digestion of wool and other substrates by Tineola proteinase and comparison with trypsin

H. Irzykiewicz

Papers

Studies on the chitinase system in bean and other seeds.

Separation of chitin oligosaccharides by thin-layer chromatography.

Detection of chitin oligosaccharides on paper chromatograms

An examination of proteolytic enzymes from several insects for collagenase activity

Studies on the digestive proteinase of clothes moth larvae (Tineola bisselliella)—II: Digestion of wool and other substrates by Tineola proteinase and comparison with trypsin