Journal of Microbiology

Journal Article

Biochemical Characterization of Chitinase 2 Expressed during the Autolytic Phase of the Inky Cap, Coprinellus congregatus: Yuri Kang , Hyewon Kim , Hyoung T. Choi; J. Microbiol. 2013;51(2):189-193. Published online April 27, 2013; DOI: https://doi.org/10.1007/s12275-013-2535-9

Abstract: Fungal cell walls consist of various glucans and chitin. The inky cap, Coprinellus congregatus, produces mushrooms at 25°C in a regime of 15 h light/9 h dark, and then the mushroom is autolyzed rapidly to generate black liquid droplets in which no cell walls are detected by microscopy. Chitinase cDNA from the mature mushroom tissues of C. congregatus, which consisted of 1,622 nucleotides (chi2), was successfully cloned using the rapid amplification of cDNA ends polymerase chain reaction technique. The deduced 498 amino acid sequence of Chi2 had a conserved catalytic domain as in other fungal chitinase family 18 enzymes. The Chi2 enzyme was purified from the Pichia pastoris expression system, and its estimated molecular weight was 68 kDa. The optimum pH and temperature of Chi2 was pH 4.0 and 35°C, respectively when 4-nitrophenyl N,N’-diacetyl-β-D-chitobioside was used as the substrate. The Km value and Vmax for the substrate A, 4-nitrophenyl N,N’-diacetyl-β-D-chitobioside, was 0.175 mM and 0.16 OD min-1unit-1, respectively.

Research Support, Non-U.S. Gov't

Growth Inhibition of the Yeast Transformant by the Expression of a Chitinase from Coprinellus congregatus: Hyangsoon Lim , Hyoung T. Choi; J. Microbiol. 2010;48(5):706-708. Published online November 3, 2010; DOI: https://doi.org/10.1007/s12275-010-0272-x

Abstract: Coprinellus congregatus generates several chitinases during its entire life cycle: at the growing hyphal stage and at the mushroom autolysis stage. We have isolated a chitinase gene (chi1) from the mushroom tissue at the autolysing stage, and constructed a chitinase expression vector to get large amount of enzyme protein. Chitinase 1 (chi1) cDNA was heterologously expressed in Saccharomyces cerevisiae by gal1 promoter. The transformants showed no specific change in growth characteristics under normal growth conditions. However the expression of the gene by the gal1 promoter in the yeast transformants resulted in complete growth inhibition, while laccase expression by the gal1 promoter showed normal growth. The chitinase activities from the transformants were also more than 3 times higher than that of the recipient strain, and the chitinase expression by the real time-PCR also showed increased expression of the chi1 in the yeast transformant. Expression of a chitinase which was produced at the mushroom autolysing stage of C. congregatus resulted in yeast growth inhibition.

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