Proteinase inhibitors in rat serum. Purification and partial characterization of three functionally distinct trypsin inhibitors

Purification and partial characterization of α1-proteinase inhibitor in the common marmoset (Callithrix jacchus)

Fecal alpha1-proteinase inhibitor (α1-PI) concentration has been to diagnose enteric protein loss in dogs and cats. Chronic lymphocytic enteritis is commonly seen in the marmoset (Callithrix jaccus) and is characterized by hypoalbuminemia. As a prelude to immunoassay development for detecting enteric protein loss, marmoset serum α1-PI was purified using immunoaffinity chromatography and ceramic hydroxyapatite chromatography. Partial characterization was performed by reducing gel electrophoresis and enzyme inhibitory assays. Protein identity was confirmed with peptide mass fingerprinting and N-terminal amino acid sequencing. Molecular mass, relative molecular mass, and isoelectric point for marmoset α1-PI were 54 kDa, 51,677, and 4.8-5.4, respectively. Trypsin, chymotrypsin, and elastase inhibitory activity were observed. N-terminal amino acid sequence for marmoset α1-PI was EDPQGDAAQKMDTSHH. In conclusion, marmoset α1-PI was successfully purified from serum with an overall yield of 12% using a rapid and efficient method. Purified marmoset α1-PI has characteristics similar to those of α1-PI reported for other species.

The major plasma kallikrein inhibitor of guinea pig plasma

A plasma kallikrein inhibitor in guinea pig plasma (KIP) was purified to homogeneity. KIP is a single chain protein and the apparent molecular weight is estimated to be 59,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In amino acid composition, KIP is similar to human and mouse alpha 1-proteinase inhibitors and mouse contrapsin. KIP forms an equimolar complex with plasma kallikrein in a dose- and time-dependent fashion. The association rate constants for the inhibition of guinea pig plasma kallikrein by KIP, alpha 2-macroglobulin, C1-inactivator and antithrombin III were 2.5 +/- 0.3.10(4), 2.4 +/- 0.4.10(4), 6.6 +/- 0.5.10(4) and 9.1 +/- 0.6.10(2), respectively. Comparison of the association rate constants and the normal plasma concentrations of the four inhibitors demonstrates that KIP is ten-times as effective as alpha 2-MG and other two inhibitors are marginally effective in the inhibition of kallikrein. KIP inhibits trypsin and elastase rapidly, and thrombin and plasmin slowly, but is inactive for chymotrypsin and gland kallikrein. These results suggest that KIP is the major kallikrein inhibitor in guinea pig plasma and the proteinase inhibitory spectrum is unique to KIP in spite of the molecular similarity to alpha 1-proteinase inhibitor.

Evaluation of assays for detecting alpha-1-protease inhibitor during purification from rat serum

We purified the R1 alpha-1-protease inhibitor from rat serum and developed a convenient assay for its detection during purification procedures. Purification was accomplished by desalting, DEAE-Sephacel, zinc chelate, and reactive green-agarose columns. The resultant antiprotease had a molecular weight of 54,000 and inhibited elastase, chymotrypsin, and trypsin. By isoelectric focusing, five bands were produced with pI values from 4.3 to 4.7. Functional assays utilizing protease substrates imbedded in agarose plates were evaluated for the ability to distinguish the R1 alpha-1-protease inhibitor from the other serum antiproteases eluted in column chromatography fractions. This technique of screening for anti-protease activity was compared to conventional spectrophotometric methods and was found to correlate well when quantifying inhibition of elastase and chymotrypsin, but not trypsin. The presence of alpha-1-protease inhibitor was most reliably detected by testing for anti-elastase activity. Technician time and expense were saved by employing protease substrate plates to test chromatogrpahy fractions. This technique may facilitate purification of other protease inhibitors.

Isolation and characterization of sheep alpha 1-proteinase inhibitor

Sheep plasma proteinase inhibitor, analogous to human alpha 1-proteinase inhibitor (alpha 1 PI), was isolated to homogeneity. Purification was achieved by using (NH4)2SO4 precipitation, concanavalin A-Sepharose chromatography, Mono Q ion-exchange chromatography and PAGE. Sheep alpha 1 PI had an Mr of 56,000, inhibited human leucocyte elastase, pig pancreatic elastase and bovine trypsin on a 1:1 molar basis and had a plasma concentration of 1.6 +/- 0.21 g/l (mean +/- S.D.). Amino acid/carbohydrate composition (15% glycosylated) was similar to that of human alpha 1 PI (16% glycosylated); N-terminal analysis to 31 residues revealed 48-52% identity between the human and sheep proteins. Sheep alpha 1 PI was susceptible to oxidative inactivation by chloramine-T. Re-activation with the use of methionine sulphoxide peptide reductase and dithiothreitol indicated the presence of a methionine residue at the active site. These results establish that sheep alpha 1 PI has functional and structural characteristics close to those of human alpha 1 PI.

Purification, characterization, and acute phase response of plasma alpha-1-antiproteinase in the hamster, Mesacricetus auratus

1. alpha-1-Antiproteinase (also called alpha-1-antitrypsin or alpha-1-proteinase inhibitor) with a molecular mass of 60 kDa was purified to apparent homogeneity from hamster plasma. 2. It inhibited elastase, chymotrypsin and trypsin, but did not significantly affect pancreatic kallikrein, plasma kallikrein or plasmin. 3. It has the same N-terminal heptapeptide sequence as that of rat alpha-1-antiproteinase. 4. Its plasma level decreased after injection of bacterial lipopolysaccharide.

A novel plaque assay system for paramyxoviruses

A combination of 5% allantoic fluid and 200 micrograms/ml DEAE-dextran with 30 mM MgCl2 used as a supplement to normal overlay medium was found to give large, clear plaques on monolayers of secondary chick embryo fibroblasts infected with avirulent strains of Newcastle disease virus which did not produce plaques without these additions. This modified overlay also allowed plaque assay of Sendai virus strain Z, and avoided any requirement for special cell lines or the use of serum-free medium.

High-molecular-mass proteinases in rabbit reticulocytes: the multicatalytic proteinase is an ATP-independent enzyme and ATP-activated proteolysis is in part associated with a cysteine proteinase complexed to alpha 1-macroglobulin

We have investigated the proteolytic degradation of [14C]methylcasein and 125I-labeled bovine serum albumin at pH 7.8 and 37 degrees C by lysates of rabbit reticulocytes purified from rabbit blood by two different procedures. (I) Lysates obtained from reticulocytes after removal of plasma and buffy coat as well as after washing of cells, degraded casein and albumin, and released from the two substrates 1.3%/h and 0.4%/h, respectively, of acid-soluble radioactivity. The activity towards both substrates was stimulated about 4-fold by ATP/Mg2+. Chromatography of whole blood on a column of cellulose prior to washing and lysis of cells had profound but differential effects on these activities in that stimulation of casein-degradation by ATP/Mg2+ was almost completely lost, whereas degradation of albumin, albeit at a low rate, was measurable in the presence of ATP/Mg2+ only. (II) Degradation of casein by these lysates is largely inhibited by a monospecific antibody against rabbit multicatalytic proteinase, whereas digestion of albumin is not affected by the antibody, either in the presence or absence of ATP/Mg2+. The latter activity is partially inhibited by a specific antibody against rabbit alpha 1-macroglobulin. (III) The immunoreactive amount of multicatalytic proteinase is about 1.2 micrograms per mg of lysate protein and almost identical in the two lysates. In contrast, the immunologically detectable levels of alpha 1-macroglobulin vary and are much lower in reticulocyte-lysates following chromatography on cellulose than in lysates from washed reticulocytes. (IV) Caseinolytic activity of multicatalytic proteinase, purified from rabbit reticulocyte lysate, is not activated by ATP/Mg2+ and the enzyme is proteolytically inactive towards albumin. On the other hand, a complex consisting of the proteinase inhibitor alpha 1-macroglobulin and the cysteine proteinase, cathepsin B, does degrade both substrates at pH 7.8, in an ATP/Mg2+-activated fashion. From these results it is concluded that the multicatalytic proteinase is an ATP-independent enzyme and a cellular constituent of rabbit reticulocytes whereas the activity stimulated by ATP/Mg2+ appears to be associated, at least in part, with a cysteine proteinase complexed to alpha 1-macroglobulin.

Immunological and chemical properties of mouse alpha 1-protease inhibitors

We previously described the isolation and purification of two similar alpha 1-protease inhibitors from mouse plasma termed alpha 1-PI(E) and alpha 1-PI(T) because of their respective affinities for elastase and trypsin. Some of the biochemical and immunological properties of these proteins are reported. Both are acidic glycoproteins with pI's of 4.1-4.2. The plasma half-life of each inhibitor, determined after administration of the 125I-protein, is approximately 4 h both in normal mice and in mice after induction of the acute phase reaction. The two proteins have almost identical amino acid compositions and similar CNBr peptide maps. Tryptic maps, however, are considerably different. Reverse-phase chromatography separated alpha 1-PI(E) into three distinct isoforms, each eluting with approximately 60% acetonitrile. Under these conditions alpha 1-PI(T) shows a single peak, clearly different from those of alpha 1-PI(E). The three alpha 1-PI(E) isoforms have the same molecular weights on sodium dodecyl sulfate-gel electrophoresis and the same tripeptide sequence at their N-terminus, and appear to be immunologically identical. Polyclonal, monospecific antibodies to each native inhibitor, prepared in rabbits, showed no cross-reactivity when tested by functional assay or crossed immunoelectrophoresis. Interestingly, each antibody recognized epitopes on the C-terminal portion of its respective antigen. These studies confirm that alpha 1-PI(E) and alpha 1-PI(T), although highly similar, are products of different genes. Like human alpha 1-PI, the two mouse inhibitors are partially inactivated by mild oxidation with chloramine-T, losing all elastase inhibitor and lesser amounts of antichymotryptic and antitryptic activity. However, unlike the human protein, neither alpha 1-PI(E) nor alpha 1-PI(T) was found to have a methionine residue at its P1 site.

Plasma protein and liver mRNA levels of two closely related murine alpha 1-protease inhibitors during the acute phase reaction

Plasma levels of alpha 1-PI(T) and alpha 1-PI(E), two closely related murine alpha 1-protease inhibitors, having affinities for trypsin and elastase, respectively, were compared to changes in specific liver mRNA levels after induction of the acute-phase reaction by subcutaneous injection of turpentine. In earlier, qualitative experiments an increase in plasma levels of alpha 1-PI(E), but not alpha 1-PI(T), during the acute-phase reaction had been shown. It is now shown that stimulation of plasma alpha 1-PI(E) levels reaches a maximum of 35-50% above baseline 12 h after induction of the acute-phase response using either a functional or immunological assay to measure protease inhibitor activity. Consistent with earlier observations, little or no change in plasma levels of alpha 1-PI(T) is seen. Determination of mRNA levels in the mouse liver specific for alpha 1-PI(E) and alpha 1-PI(T) was accomplished using a cell-free translation system followed by immunoprecipitation of the 35S-labeled protease inhibitors. The apparent Mr's of alpha 1-PI(E) and alpha 1-PI(T) synthesized in vitro are 42K and 46K, respectively. Apparent Mr's of the native proteins in plasma are 55K and 65K. Unexpectedly, mRNA levels for both alpha 1-PI(E) and alpha 1-PI(T) were found to increase after induction of the acute-phase reaction. Maximal stimulation for both mRNAs was approximately 300% and occurred 9 h after turpentine administration. Under these conditions, levels of translatable albumin mRNA in the mouse liver decreased to 40% of baseline in 6-9 h.

Plasma proteinase inhibitors in Morris hepatoma-bearing rats: changes in the blood level and synthesis in tissue slices

The antiproteinase activities against trypsin, chymotrypsin, elastase, papain and rat leucocyte proteinases were determined in plasma from control and Morris hepatoma-bearing rats. Bovine trypsin and chymotrypsin were similarly inhibited by the two types of plasma whereas porcine pancreatic elastase, papain and rat leucocyte neutral proteinases were more efficiently inhibited by plasma from tumour-bearing rats. The increased plasma concentrations of some proteinase inhibitors, as determined by rocket immunoelectrophoresis, are suggested to be responsible for the observed differences in inhibition. The highest increases in plasma of tumour-bearing rats were observed for alpha 2-macroglobulin and alpha 1-acute-phase globulin. The synthesis and secretion of six proteinase inhibitors: antithrombin III, alpha 1-proteinase inhibitor, alpha 1-macroglobulin, alpha 2-macroglobulin, alpha 1-acute-phase globulin and haptoglobin, as well as albumin, were measured in tissue slices from rat liver and Morris hepatoma after incubation with [14C]leucine. Local inflammation inflicted upon the tumour-bearing rats increased formation of acute-phase proteins in liver slices but not in hepatoma slices.

Identification of four distinct serine proteinase inhibitors in rat skeletal muscle

The serine proteinase inhibitory capacity in the cytosolic fraction of rat skeletal muscle tissue is accounted for by several discrete inhibitory activities. Three of these activities are identical with the proteinase inhibitors alpha 1-proteinase inhibitor, rat proteinase inhibitor I and rat proteinase inhibitor I I respectively, which have been recently characterized as major serine proteinase inhibitors in rat serum (Kuehn, L., Rutschmann, M., Dahlmann, B. and Reinauer, H. (1984) Biochem. J. 218, in the press). The other inhibitor molecule, having an Mr of about 15 000, appears to be an endogenous inhibitor.