3.2.1.18 exo-alpha-sialidase Clostridium chauvoei 3.2.1.18 exo-alpha-sialidase Clostridium chauvoei Jakari 3.2.1.18 exo-alpha-sialidase Clostridium chauvoei NC08596 4.2.2.1 hyaluronate lyase Clostridium chauvoei