The effects of N-substitution of chitosan and the physical form of the products on the rate of hydrolysis by chitinase from Streptomyces griseus

Abstract

N-Formyl, N-chloroacetyl, N-glycyl, N-isobutyryl, and N-pentanoyl derivatives of chitosan have been prepared. N-Acetylchitosan was the derivative most susceptible to chitinase from Streptomyces griseus and lysozyme from chicken egg-white, but the susceptibility was not restrictive. The relative rates of hydrolysis by chitinase with respect to R in the RCONH group were CH 3 > CH 3CH 2 > H > CH 3CH 2CH 2 > (CH 3) 2CH > NH 2CH 2 > ClCH 2. Neither enzyme hydrolysed chitosan or its N-methylene, N-benzylidene, N-benzoyl, N-nicotinyl, and N-fatty acyl (C 5C 18) derivatives, and lysozyme did not hydrolyse N-butyrylchitosan. N-Acetylhexanoyl-chitosans, which had d.s. ratios of ~0.7: ~0.3 and ~0.3; ~0.7, were hydrolysed at ~0.75 and ~0.04 of the rate of N-acetylchitosan (powder) by chitinase. O-Acylation of N-acylchitosans caused a decrease in the rates of hydrolysis by chitinase. N-Acetylchitosan gels were hydrolysed at 8–13 times the rate for crab-shell chitin. These results indicate that not only N- and O-substituents but also the physical form of the substrates influence the rates of hydrolysis by these enzymes.