Isolation and partial characterization of a low molecular weight trypsin inhibitor from human urine

Identification of uronic-acid-rich protein as urinary bikunin, the light chain of inter-alpha-inhibitor

Uronic-acid-rich protein (UAP) is a urinary glycoprotein that inhibits calcium oxalate crystallization in vitro. It shows a structural similarity to bikunin, a component of inter-alpha-inhibitor (IalphaI) known for its inhibition of the action of many serine proteinases like trypsin and chymotrypsin. To clarify the relationship between these macromolecules, UAP, IalphaI, urinary bikunin, and plasma bikunin were purified and studied. Their calcium oxalate crystallization inhibitory activity was assayed before and after treatment with chondroitinase AC and pronase. Their molecular mass was determined by using SDS/PAGE before and after these treatments. Polyclonal bikunin antibody was used on Western blots for immunological identification. The partial amino acid sequence of UAP before and after chondroitinase treatment was determined. Also, the antitryptic activity of UAP was measured and compared to that of bikunin, which is responsible for the antiprotease activity of IalphaI. UAP exhibited a strong calcium oxalate crystallization inhibitory activity. IalphaI and both bikunins were less inhibitory. Chondroitinase AC had no effect on inhibitory activity of these proteins even when their molecular mass changed. However, after pronase treatment, the inhibitory activity of both bikunins and UAP was completely destroyed. The antitryptic activity of UAP was found to be 0.78 U/mg which is lower than that of bikunin which is about 1.9 U/mg. On Western blotting, bikunin antibody immunoreacted with UAP and both urinary and plasma bikunins. Partial amino acid sequence confirmed the identity of UAP as urinary bikunin.

Cancer-related urinary proteinase inhibitor, EDC1: a new method for its isolation and evidence for multiple forms

During the past several years, numerous laboratories have reported isolation and purification of proteinase inhibitors from human urine. Many of these molecules were incompletely characterized and some of them may have been artifacts in part because of harsh procedures used for their isolation. Consequently, there is disagreement and confusion regarding the biochemical characteristics of these inhibitors. We previously reported the isolation of a proteinase inhibitor, EDC1, from the urine of a leukemic patient. This molecule, M(r) 30 kDa, was antigenically related to plasma inter-alpha-trypsin inhibitor (IATI) and inhibited the growth of a virally transformed B cell line. Immunoreactive EDC1 was also the major component of low molecular weight proteinuria observed in cancer patients. We now report a new method for the isolation of EDC1 from urine of patients with adenocarcinomas of colon and lung and melanoma and compare its partial amino acid sequence with that of HI 30, a proteinase inhibitor previously isolated from pooled normal urine by Hochstrasser et al. [Hoppe-Seyler's Z Physiol Chem 357:153-162, 1976]. Our method involves i) a batchwise cation exchange, ii) gel filtration chromatography, iii) anion exchange chromatography on FPLC, and iv) reverse phase C18 chromatography on HPLC. This method is mild and results in an overall yield of 0.4 to 1.2 mg of EDC1/liter urine. On the basis of the partial N-terminal amino acid sequence of its N terminal (38 residues) and middle regions (29 residues), EDC1 appears to be identical with HI30. Surprisingly, during this isolation procedure, another proteinase inhibitor, M(r) 22 kDa, which cross-reacted with antisera to EDC1 and IATI, was also isolated. The 22 kDa molecule was a major component of the IATI related urinary molecules and was identical with the 30 kDa EDC1 in which first the 15 N terminal residues were clipped. The lower M(r) inhibitor was not an artifact formed during storage or isolation procedure because the Western blot analysis of fresh cancer and normal urine revealed the 30 and 22 kDa molecules. Thus, both the 30 kDa EDC1 (or HI30) and its clipped variant, the 22 kDa molecule, are physiologic components of IATI related urinary proteinase inhibitors and excretion of both forms may be increased in patients with advanced cancer.

In vivo metabolism of inter-alpha-trypsin inhibitor and its proteinase complexes: evidence for proteinase transfer to alpha 2-macroglobulin and alpha 1-proteinase inhibitor

Inter-alpha-trypsin inhibitor was purified by a modification of published procedures which involved fewer steps and resulted in higher yields. The preparation was used to study the clearance of the inhibitor and its complex with trypsin from the plasma of mice and to examine degradation of the inhibitor in vivo. Unlike other plasma proteinase inhibitor-proteinase complexes, inter-alpha-trypsin inhibitor reacted with trypsin did not clear faster than the unreacted inhibitor. Studies using 125I-trypsin provided evidence for the dissociation of complexes of proteinase and inter-alpha-trypsin inhibitor in vivo, followed by rapid removal of proteinase by other plasma proteinase inhibitors, particularly alpha 2-macroglobulin and alpha 1-proteinase inhibitor. Studies in vitro also demonstrated the transfer of trypsin from inter-alpha-trypsin inhibitor to alpha 2-macroglobulin and alpha 1-proteinase inhibitor but at a much slower rate. The clearance of unreacted 125I-inter-alpha-trypsin inhibitor was characterized by a half-life ranging from 30 min to more than 1 h. Murine and human inhibitors exhibited identical behavior. Multiphasic clearance of the inhibitor was not due to degradation, aggregation, or carbohydrate heterogeneity, as shown by competition studies with asialoorosomucoid and macroalbumin, but was probably a result of extravascular distribution or endothelial binding. 125I-inter-alpha-trypsin inhibitor cleared primarily in the liver. Analysis of liver and kidney tissue by gel filtration chromatography and sodium dodecyl sulfate gel electrophoresis showed internalization and limited degradation of 125I-inter-alpha-trypsin inhibitor in these tissues. No evidence for the production of smaller proteinase inhibitors from 125I-inter-alpha-trypsin inhibitor injected intravenously or intraperitoneally was detected, even in casein-induced peritoneal inflammation. No species of molecular weight similar to that of urinary proteinase inhibitors, 19,000-70,000, appeared in plasma, liver, kidney, or urine following injection of inter-alpha-trypsin inhibitor.

Identification of a specific interleukin 1 inhibitor in the urine of febrile patients

The urine of febrile patients has been found to contain high concentrations of an inhibitor of interleukin 1 (IL-1)-induced thymocyte proliferation. The inhibitor is specific for IL-1 and does not block the effects of interleukin 2 (IL-2) or phytohemagglutin (PHA) on thymocytes, and it is not nonspecifically toxic for these cells. IL-1 inhibitor can be found in the urine of normal individuals and afebrile patients, but is present in increased concentrations in the urine of patients with fever of diverse etiologies. Preliminary physicochemical characterization indicates that the inhibitor is a 20-40-kdalton protein.

Purification and partial characterization of two forms of urinary trypsin inhibitor

Crude urinary trypsin inhibitor was obtained by DEAE-cellulose column chromatography from normal fresh urine. By the purification of the crude urinary inhibitor on successive chromatography methods using Sephacryl S-200, DEAE-cellulose, CM-Sepharose CL-6B and Sephadex G-100, we detected two forms of urinary trypsin inhibitor: form I and form II. The specific activity of form I increased approx. 4-fold with a recovery of 60%, as compared to that of crude urinary trypsin inhibitor. N-terminal amino acids of form I and form II were determined to be alanine and valine, respectively. Molecular weights of forms I and II were estimated to be 67000 and 28000 by gel filtration on Sephadex G-100 and to be 43000 and 19000 by SDS-polyacrylamide gel electrophoresis. S-carboxymethylated form I migrated as a single band corresponding to a molecular weight of 59000 in SDS-polyacrylamide gel electrophoresis. From the results of the determination of a single N-terminal amino acid of form I and a single band of S-carboxymethylated form I, it is indicated that it is composed of single polypeptide chain. And the present study suggests that form I is a native form of trypsin inhibitor in normal human urine and form II is a fragmented product from form I in the purification steps.

Proteins binding to kallikrein and esterase A2 in the urine of salt-sensitive and salt-resistant rats

Iodine-labeled ([125I]) rat urinary kallikrein and rat urinary TAME esterase A2 were used as probes to look for urinary and plasma proteins that bind to these enzymes. Such proteins are presumptive enzyme inhibitors. Complexes formed with labeled enzymes were identified by polyacrylamide gel electrophoresis followed by autoradiography. Urine from young (6 weeks old) Dahl salt-sensitive (S) rats showed no, or only traces, of protein binding to kallikrein. Concomitant with the slow development of hypertension and proteinuria in S rats fed normal rat chow, one of the six kallikrein-binding proteins demonstrable in plasma was readily found in S-rat urine. This kallikrein-binding protein was called "KBP-1." R rats showed either no or much less KBP-1 in the urine, compared to S rats up to 5 months of age. A partly purified preparation of KBP-1 was shown to inhibit the TAME esterase activity of rat urinary kallikrein in the radiometric TAME assay. Urine of proteinuric S rats also contained two TAME esterase-binding proteins, TEBP-1 and TEBP-2, detected with the [125I]-esterase A2 probe. As S rats aged from 3 to 8 months, free KBP-1 disappeared from the urine in spite of increased and marked proteinuria and the continued presence of KBP-1 in plasma. Concomitant with this age-related loss of urinary KBP-1 there was a marked shift in S urinary proteins binding to [125I]-esterase A2 from TEBP-1 to TEBP-2. It was speculated that KBP-1 and TEBP-1 were the same protein detectable with either labeled kallikrein or labeled esterase A2. The concomitant disappearance of free KBP-1 (TEBP-1) and the appearance of free TEBP-2 in the urine of old, hypertensive, proteinuric S rats suggests that: 1) most of the KBP-1 (TEBP-1) is bound to enzyme(s) in old rats; or 2) KBP-1 (TEBP-1) is largely converted to TEBP-2 in old rats; or 3) both are true and that binding of KBP-1 (TEBP-1) to enzymes is associated with the generation of TEBP-2.