Purification and characterization of the sunflower seed (Helianthus annuus L.) major aminopeptidase

The sunflower seed (Helianthus annuus L.) major peptidase was purified to molecular homogeneity. It is an 80 kDa enzyme with pI of 4.6 and optimal activity at pH 7.5-8.0 and 45-50A degrees C. It is a thiol-dependent aminopeptidase hydrolyzing peptides in a step-by-step manner as cleaving after the N-terminal amino acid residue of the substrate. It requires substrate acyl parts with a free amino group in either alpha- or beta-position and l-configuration of the adjacent carbon atom. The enzyme prefers amino acid residues with bulky hydrophobic side chains at P-1-position and its catalytic efficacy is affected by the structure of both P-1 and P-1' parts of the substrate.