Two forms of alpha-amylase in mantle tissue of Mytilus galloprovincialis: purification and molecular properties of form II.

alpha-Amylase activity has been shown for the first time in a non-digestive tissue from Mytilus galloprovincialis. alpha-amylase from mussel mantle tissue has been purified by affinity chromatography on insoluble starch, followed by gel-filtration chromatography on Superdex-200. The chromatographic and electrophoretic behaviour of M. galloprovincialis alpha-amylase and stability characteristics suggest two forms of this enzyme: one form forming stable aggregates (form I) and a monomeric form (form II) that is more abundant, active and unstable. Both forms show an inverse quantitative variation. Purified form II was highly unstable and the molecular mass was estimated to be 66 kDa by sodium dodecyl sulphate (SDS)-gel electrophoresis. Maximum activity was noted at pH 6.5 and 35 degrees C.