Carbohydrate esterase family 4 enzymes: substrate specificity.

The substrate specificity of selected enzymes classified under Carbohydrate Esterase family 4 (CE4) has been examined. Chitin deacetylase from Mucor rouxii and both a native and a truncated form of acetyl xylan esterase from Streptomyces lividans were found to be active on both xylan and several soluble chitinous substrates. Furthermore, the activities of all enzymes examined were significantly increased in the presence of Co(2+) when chitinous substrates were employed. However, the presence of this metal ion did not result in enhancing the activities of the enzymes when xylan was used as substrate. An acetyl xylan esterase from Bacillus pumilus, classified under Carbohydrate Esterase family 7, was found to be inactive towards all chitinous substrates tested. Finally, all enzymes examined were inactive towards cell wall peptidoglycan.