Isolation, Purification, and the Amino Acid Sequence of a Secretory Trypsin Inhibitor from the Chicken Pancreas

Abstract

A trypsin inhibitor is secreted in the pancreatic juice of the chick. Extracts from tissue have an inhibitor that corresponds to the secreted inhibitor on the basis of chromatography on DEAE-cellulose. The secretory inhibitor was purified by anion- and cation-exchange chromatography and by preparative isoelectric focusing. The purified inhibitor has 69 amino acids and is highly homologous with the secretory inhibitor from the turkey pancreas.

Ratio of Digestive Enzymes in the Chick Pancreas

“…In addition to the enzymes reported in that study, an elastase, three forms of chymotrypsin, and a secretory trypsin inhibitor have also been found in the chick in the present study ( Figure 1, Table 1). The trypsin inhibitor secreted by the chick pancreas (Pubols, 1990) is highly homologous with inhibitors secreted by the pancreas from mammals and the turkey (Bogard and Laskowski, 1979;Laskowski et al, 1987). An earlier report from the author's laboratory had indicated that a similar profile of enzymes was present in pancreatic juice from the chick (Dal Borgo et al, 1968a).…”

“…The mixture of trypsin and trypsin inhibitor was allowed to react for 1 min at room temperature (23 C) before assay. For standardization, the amount of inhibitor required to reduce the rate of TAME hydrolysis by 50% was used for assays (Greene et al, 1966;Pubols, 1990).…”

A Kazal-type serine proteinase inhibitor from chicken liver (clTI-1)

“…clTI-1 reveals close homology to the chicken Kazal-type serine proteinase inhibitor precursor [35], which is similar to the proteinase inhibitor isolated from seminal plasma of turkey [11]. High homology to the other members of Kazal-type family, especially to acrosin-trypsin inhibitors [36,37], pancreatic secretory trypsin inhibitors [27,28,31,32,[38][39][40], ovomucoids, and chicken ovoinhibitor, was revealed as well (Fig. 8).…”

“…clTI-1 consists of a single polypeptide chain of 55 (54) amino acids. The amino acid composition of purified inhibitor is similar to that of Kazal-type inhibitors of other species [27][28][29][30][31][32][33][34]. It contains six Cys residues, suggesting that three disulfide bonds are present in the three-dimensional structure.…”

“…Kt-SPI -Kazal-type serine proteinase inhibitor [35]; mgSPI -serine proteinase inhibitor from Meleagris galopado [11]; mfATI II -acrosin-trypsin inhibitor from Macaca fascicularis [36]; HUSI II -human seminal inhibitor [37]; hPSTI -human PSTI [38]; hrPSTI -horse PSTI [39]; bPSTI -bovine PSTI [29]; pPSTI -porcine PSTI [28]; rPSTI -rat PSTI [40]; mdPSTI -PSTI from Monodelphis domestica [39]; PEC-60 -peptide from porcine intestine [41]; MPGC60 -peptide from mouse intestine [42]; EPP -peptide from eel pancreas [43]; OPTI -ostrich PSTI [32]; CPTI -chicken PSTI [31].…”