Aspects of Cellulin Deposition and Chitin Biosynthesis in the Leptomitaceae

Huizar, H. Elaine; Aronson, Jerome M.

doi:10.2307/3793057

Cited by 6 publications

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“…The chitin synthase of S. monoica exhibited properties similar to those reported for chitin synthase of other fungi such as zymogenicity, stimulation by Mg2+, apparent K , for UDP-GlcNAc and inhibition by polyoxin (Ruiz-Herrera et al, 1984;Gay et a/., 1989;Gooday, 1990). The specific activity of chitin synthase from S. monoica was lower than that observed with enzymes from typical chitinous fungi, but higher than those characterized in other Oomycetes : Leptomitus, Apodachfyeffa or Apodachfya (Huizar & Aronson, 1986, 1987.…”

Section: Introductioncontrasting

confidence: 57%

The properties and localization of Saprolegnia monoica chitin synthase differ from those of other fungi

1997

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a n d Sa I om 6 n B a r t n i c k i -G a rc fa3 The presence of non-fibrillar a-chitin in cellulosic fungi (class Oomycetes) poses intriguing questions as to i t s role, subcellular localization and evolutionary significance. Previous studies reported on the similarity of chitin synthase from Saprolegnia monoica with that of other fungi. The present work describes important dissimilarities. There was no evidence that the chitin synthase of S. monoica was present in small low-density vesicles (chitosomes). Chitin synthase sedimented with membranous components of high specific gravity (sp. gr. 1-177) that could be partially but distinctly separated from membranes harbouring most of the 1,3-&glucan synthase in the cell (sp. gr. 1.158).In contrast to other fungi, the chitin synthase from 5. monoica was greatly stimulated by digitonin: both membrane-bound and dissociated chitin synthase showed little activity in the absence of digitonin. As in other fungi, the chitin synthase from S. monoica was solubilized by digitonin and remained zymogenic after dissociation. However, unlike the enzyme from other fungi, the solubilized chitin synthase of S. monoica had a lower sedimentation coefficient, was not stimulated by phospholipids and was not inhibited by high concentrations of digitonin. Unlike the enzyme from Mucor rouxii, the solubilized chitin synthase from 5. monoica did not bind to a cation exchanger. The enzyme was partially purified by a four-step scheme that included sucrose density-gradient centrifugation, a single passage through a strong anion exchanger and two consecutive passages through a weak anion exchanger. The final preparation contained five to seven polypeptide bands that cochromatographed with the chitin synthase activity, some of which may be part of a presumed chitin synthase macromolecular complex.

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Section: Introductioncontrasting

confidence: 57%