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The nature of the collagenolytic cathepsin of rat liver and its distribution in other rat tissues.

ABSTRACT: 1. An enzyme present in rat liver extracts degraded insoluble collagen maximally at pH3.5. Collagenolytic activity was more abundant in kidney, spleen and bone marrow and was also present in decreasing concentrations in ileum, lung, heart, skin and muscle. 2. The crude collagenolytic cathepsin was activated by cysteine and dithiothreitol, but not by 2-mercaptoethanol. Iodoacetamide, p-chloromercuribenzoate and 7-amino-1-chloro-3-l-tosylamidoheptan-2-one hydrochloride inhibited the enzyme. Zn(2+), Fe(3+) and Hg(2+) ions were strongly inhibitory, but Ca(2+), Co(2+), Mg(2+) and Fe(2+) ions had little or no effect. EDTA was an activator of the enzyme. Inhibitors of cathepsin B were found to enhance collagenolysis, but phenylpyruvic acid, a cathepsin D inhibitor, inhibited the enzyme. Di-isopropyl phosphorofluoridate had no effect. 3. Collagenolysis at pH3.5 and 28 degrees C was restricted to cleavage of the telopeptide region in insoluble collagen, and the material that was solubilized consisted mostly of alpha-chains. 4. The collagenolytic cathepsin was separated from cathepsins B2 and D by fractionation on Sephadex G-100 and a partial separation from cathepsin B1 was obtained by chromatography on DEAE-Sephadex. 5. The function of the collagenolytic cathepsin in the catabolism of collagen is discussed in relation to the action of the other lysosomal proteinases and the neutral collagenase.

SUBMITTER: Etherington DJ

PROVIDER: S-EPMC1178767 | biostudies-other | 1972 May

REPOSITORIES: biostudies-other

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Project description:The aim of the work was to identify and characterize the cysteine proteinases of bone tissue, as these enzymes appear necessary for bone resorption. Three cysteine-dependent proteolytic activities were separated from a homogenate of mouse calvaria by a fractionation procedure involving (NH4)2SO4 precipitation, gel filtration and ion-exchange chromatography. The first two are typical cathepsins B and L with respect to (1) their reactivity with anti-(cathepsin B) and anti-(cathepsin L) antibodies respectively, (2) their relative rate constants for inhibition by benzyloxycarbonyl-Phe-Phe-CHN2 and L-3-carboxy-trans-2,3-epoxypropionyl-L-leucylamido-(4-guanid ino)butane and (3) their enzymic properties, such as the higher activities of cathepsin L against collagen and gelatin as compared with cathepsin B, and the fact that benzyloxycarbonyl-Arg-Arg 4-methoxy-2-naphthylamide is hydrolysed only by cathepsin B. Cathepsin L was mainly recovered in its precursor form, as indicated by its apparent 40 kDa molecular mass and its relative stability at pH 7.2. The third enzyme is a cathepsin L-like proteinase with an apparent molecular mass of 70 kDa. It is immunoprecipitated by anti-(cathepsin L) antibodies, and appears as the 25 kDa band of mature cathepsin L in Western blots. It further resembles (pro)cathepsin L with regard to its activities against synthetic substrates and proteins such as collagen, and with regard to its response to various inhibitors. However, unlike (pro)cathepsin L, it is eluted as a 70 kDa protein on gel filtration (even in the presence of 1% Brij or 1 M-NaCl), it is stable at pH values as high as 9, and it exhibits stronger affinity for phenyl-Sepharose. It might thus result from a strong complex between mature cathepsin L and another entity that confers stability at alkaline pH and favours hydrophobic interactions. This 70 kDa activity was also detected in mouse muscle and long bones of Ca(2+)-deficient chicks but not in mouse liver, spleen or kidney.

Project description:BackgroundA family of secreted cathepsin L proteases with differential activities is essential for host colonization and survival in the parasitic flatworm Fasciola hepatica. While the blood feeding adult secretes predominantly FheCL1, an enzyme with a strong preference for Leu at the S2 pocket of the active site, the infective stage produces FheCL3, a unique enzyme with collagenolytic activity that favours Pro at P2.Methodology/principal findingsUsing a novel unbiased multiplex substrate profiling and mass spectrometry methodology (MSP-MS), we compared the preferences of FheCL1 and FheCL3 along the complete active site cleft and confirm that while the S2 imposes the greatest influence on substrate selectivity, preferences can be indicated on other active site subsites. Notably, we discovered that the activity of FheCL1 and FheCL3 enzymes is very different, sharing only 50% of the cleavage sites, supporting the idea of functional specialization. We generated variants of FheCL1 and FheCL3 with S2 and S3 residues by mutagenesis and evaluated their substrate specificity using positional scanning synthetic combinatorial libraries (PS-SCL). Besides the rare P2 Pro preference, FheCL3 showed a distinctive specificity at the S3 pocket, accommodating preferentially the small Gly residue. Both P2 Pro and P3 Gly preferences were strongly reduced when Trp67 of FheCL3 was replaced by Leu, rendering the enzyme incapable of digesting collagen. In contrast, the inverse Leu67Trp substitution in FheCL1 only slightly reduced its Leu preference and improved Pro acceptance in P2, but greatly increased accommodation of Gly at S3.Conclusions/significanceThese data reveal the significance of S2 and S3 interactions in substrate binding emphasizing the role for residue 67 in modulating both sites, providing a plausible explanation for the FheCL3 collagenolytic activity essential to host invasion. The unique specificity of FheCL3 could be exploited in the design of specific inhibitors selectively directed to specific infective stage parasite proteinases.

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The nature of the collagenolytic cathepsin of rat liver and its distribution in other rat tissues.

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