Purification and amino acid analysis of plasma acid stable trypsin inhibitor.

Acid stable trypsin inhibitor (ASTI), with a molecular weight of about 85,000 by gel filtration, specific activity of 1,498 U/mg protein and pI of 1.6, from renal failure patient plasma was first purified. The amino acid composition of the purified ASTI was found to be that of a Gly- and Glu-rich protein which lacked His, closely resembling that of urinary trypsin inhibitor. The NH2-terminal amino acid sequence was Ala-Val-Leu-Pro-Gln-Glu- Glu-Glu-Gly-X-Gly-Gly-Gly-Gln-Leu-Val-Thr-Glu-Val-Thr-Lys-Lys-Glu- Asp-Ser-Ser-Gln-Leu-Gly-Tyr-Ser-Ala-Gly-Pro.