ACT_SITE 21; /note="Nucleophile"; /evidence="ECO:0000255|PROSITE-ProRule:PRU00331"; ACT_SITE 118; /note="Proton acceptor"; /evidence="ECO:0000255|PROSITE-ProRule:PRU00331"; ACT_SITE 133; /evidence="ECO:0000250|UniProtKB:P54252, ECO:0000255|PROSITE-ProRule:PRU00331"