Characterization of EprA, a major extracellular protein of Oenococcus oeni with protease activity

Extracellular proteins from Oenococcus oeni, a wine-making bacterium, were isolated during growth on media differing by their nitrogen content. Analysis by two-dimensional electrophoresis revealed a low number of protein signals. Among the main spots, one signal corresponded to a single protein, which contained a lysine repeat domain characteristic of cell-wall hydrolases. We demonstrated that this major protein, named EprA, was able to hydrolyse several proteins. The heterologous production of this protein in Escherichia coli confirmed the protease activity of EprA. With a MW of 21.3 kDa and a pI of 5.3, EprA presents optimal activity at pH 7.0 and 45 °C. This O. oeni protease differs from all lactic acid bacteria proteases so far identified, and thus this bacterium possesses at least three proteases for wine protein hydrolysis.