Isolation of Acid-Resistant Urinary Trypsin Inhibitors by High Performance Liquid Chromatography and Their Characterization by N-Terminal Amino-Acid Sequence Determination

Abstract
Two crude fractions of acid-resistant trypsin inhibitors (apparent MW 44 and 20 kDaltons) were prepared from human urine by gel permeation chromatography. From both preparations the pure inhibitors were isolated by high performance liquid chromatography (HPLC). Their N-terminal amino-acid sequences were determined and compared with those of HI-30 and HI-14 as isolated by reversible binding to either immobilized trypsin or immobilized chymotrypsin. The N-terminal amino-acid sequence of the high-MW inhibitor UI-I isolated by HPLC was identical with those of HI-30 and UI-C-I isolated via immobilized trypsin or chymotrypsin. The low-MW inhibitors UI-II and UI-C-II differ from HI-14 by the N-terminal extension Glu-Val-Thr-Lys- when obtained by HPLC or by the extension Thr-Lys- when obtained via immobilized chymotrypsin. The comparison of these N-terminals with the amino-acid sequence of HI-30 (Ala1-...-Val16-Thr-Glu-Val-Thr-Lys-HI-14) defines the low-MW urinary trypsin inhibitors as proteolytic degradation products of the high-MW urinary inhibitor. Proteolysis may occur at different bonds. The existing discrepancies in molecular architecture and in MW of the urinary trypsin inhibitors are discussed.

This publication has 18 references indexed in Scilit: