[The role of the N-terminal amino group in the activity of pancreatic lipase].

Chemical modification of porcine pancreatic lipase by increasing amounts of [2, 3-3H] succinic anhydride revealed the presence of two highly reactive amino groups in the enzyme. The initial modification of lipase with p-nitrophenyl acetate enabled practically selective modification of a single amino group in the enzyme molecule. The lipolytic activity of succinylated enzymes in micellar solution of sodium taurodeoxycholate in the presence of 10-fold excess of colipase was completely suppressed, and the monosuccinylated lipase did not bind to colipase-agarose column or to the surface of tributyrin emulsion in micellar solution of taurodeoxycholate in the presence of colipase. It was concluded that the N-terminal alpha-amino group of the enzyme is essential for lipase-colipase complex formation in true solution and for enzyme binding to the bile salt covered substrate surface in the presence of colipase.