STEREOSPECIFICITY OF HUMAN HEN AND PAPAYA LYSOZYMES

Lysozymes from human, hen egg white, and papaya sources have been studied in regard to the stereospecificity of their rupture of the β-(l-4)-linked glycoside bonds of substrates. The human and hen enzymes catalyze extensive transglycosylation in addition to hydrolysis. Use has been made of this to quantitate the formation of methyl glycosaminide(s) during cleavage of 14C-labeled chitobiose in the presence of methanol. In this manner it could be shown that human and hen lysozymes catalyze cleavage of the disaccharide with retention of configuration to an extent of at least 99.9 and 99.7%, respectively. Papaya lysozyme does not catalyze glycosyl transfer. In addition it differs from the human and hen enzymes in that inversion of configuration prevails in the products obtained from degradation of chitotetraose. The findings are discussed in relation to possible mechanistic pathways for catalysis by the three lysozymes. © 1969, American Chemical Society. All rights reserved.