Molecular Characterization of a NovelN-Acetylneuraminate Lyase fromLactobacillus plantarumWCFS1

Abstract

ABSTRACTN-Acetylneuraminate lyases (NALs) or sialic acid aldolases catalyze the reversible aldol cleavage ofN-acetylneuraminic acid (Neu5Ac) to form pyruvate andN-acetyl-d-mannosamine (ManNAc). In nature,N-acetylneuraminate lyase occurs mainly in pathogens. However, this paper describes how anN-acetylneuraminate lyase was cloned from the human gut commensalLactobacillus plantarumWCFS1 (LpNAL), overexpressed, purified, and characterized for the first time. This novel enzyme, which reaches a high expression level (215 mg liter−1culture), shows similar catalytic efficiency to the best NALs previously described. This homotetrameric enzyme (132 kDa) also shows high stability and activity at alkaline pH (pH > 9) and good temperature stability (60 to 70°C), this last feature being further improved by the presence of stabilizing additives. These characteristics make LpNAL a promising biocatalyst. When its sequence was compared with that of other, related (real and putative) NALs described in the databases, it was seen that NAL enzymes could be divided into four structural groups and three subgroups. The relation of these subgroups with human and other mammalian NALs is also discussed.