Purification and Properties of a Proteinase from a Marine Luminous Bacterium, Vibrio harveyi Strain FLA-11

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A proteolytic, marine luminous bacterium was isolated from seawater and identified as Vibrio harveyi strain FLA-11. A proteinase from this strain, with a specific activity 61-fold higher than that of the culture supernatant, was purified to homogeneity. The purified enzyme had a molecular weight of 84, 000, comprising a tetramer of 21, 000 molecular weight subunits. The enzyme was most active at pH 8.0 and 55°C, and stable below 40°C. The enzyme activity was completely inhibited by EDTA, orthophenanthrolin and phosphoramidon. Metal ions such as Cu²⁺, Hg²⁺, Ni²⁺, Cd²⁺ and Co²⁺ also inhibited the activity. These results indicate that this enzyme is a metal-chelatersensitive, alkaline proteinase.