Transglutaminase from Streptoverticillium ladakanum and application to minced fish product

The transglutaminase (TGase) from Streptoverticillium ladakanum was purified to electrophoretic homogeneity after ammonium sulfate fractionation and Blue Sepharose Fast Flow chromatography. The molecular weight of the purified TGase was 30.5 kDa estimated by Superdex 75HR gel filtration, and 37.5 kDa by SDS-PAGE. This enzyme, with optima at pH at 6.0 and 50°C was very stable at pH 5.0–7.0. It was strongly inhibited by PCMB, PMSF, Pb²⁺, Zn²⁺ and Cu²⁺, but not affected by EDTA and Ca²⁺. This suggested that the purified TGase was calcium-independent and its active center contained cysteine. It catalyzed the crosslinking of fish myosin heavy chain and substantially increased the gel strength of mackerel surimi.