engleski

Properties of Prolyl Aminopeptidases from Streptomyces rimosus

Peptide bonds formed by proline are hard to hydrolyze by most of the common peptidases. This results in accumulation of proline containing peptides during industrial processes such as preparation of protein hydrolysates and cheese ripening. As some of the peptides have bitter taste, they are not desirable in products, what raises an interest for enzymes that might degrade them. Among others, prolyl aminopeptidases (Pro-AP) are enzymes that can hydrolyze peptides having proline as N-terminal amino acid. In our previous work we have found within mycelium of bacterium Streptomyces rimosus, two Pro-APs and described some of their basic properties. As from the practical point of view their substrate specificity would have the most important role, we have undertaken its determinatio. Starting from the extracts of S. rimosus mycelia and applying known methods for protein separation the enzymes splitting proline-2-naphthylamide were purified as previously described. Their substrate specificity was investigated using a series of amino acid-2-naphthylamides (2NA) and peptides of various composition and size. Both enzymes hydrolyzed only proline and hydroxyproline-2NA. They also degraded peptides with free proline at the N-terminal position but not N-CZB-Pro-Ala. The best substrates were dipeptides and tripeptides. With increase of peptide size the ability to bind to the enzyme decreased and octa- and decapeptides were not substrates. As second position aromatic, basic and aliphatic amino acids were permitted. Acording to their specificity both S. rimosus prolyl-APs can contribute to final steps of protein degradation to completion.

prolyl aminopeptidase ; Streptomyces rimosus ; intracellular aminopeptidase

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