Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several methods have been used to study the distribution of the semicarbazide-sensitive amine oxidase (SSAO) within the wall of the rat aorta. After separation of the smooth muscle-containing layers of the tunica media from the connective tissue of the tunica adventitia, much higher specific enzyme activity (measured with 1 microM benzylamine) was found in homogenates of the media than of adventitia. Similar results were obtained for MAO-A (with 1 mM 5-HT as substrate). SSAO activity was also considerably higher in homogenates of cells (predominantly smooth muscle) isolated from medial tissue by enzymatic dissociation with collagenase and elastase compared with homogenates of cells (mostly of connective tissue origin) from the adventitia. Histochemical staining resulting from SSAO activity (with benzylamine as substrate) occurred predominantly and intensely over the tunica media in rat aortic sections, although some occasional staining of adventitial sites was also observed. Staining was prevented by the SSAO inhibitors hydroxylamine (1 microM) and semicarbazide (1 mM), but not by the MAO inhibitor, clorgyline (1 mM). These results indicate that SSAO is associated predominantly, although not exclusively, with the smooth muscle cells in the rat aorta. Our findings that beta-aminopropionitrile (BAPN) is a reversible, competitive inhibitor (Ki around 2 X 10(-4)M) of SSAO, in contrast to the irreversible inhibition of the connective tissue lysyl oxidase by BAPN reported by others, provides further evidence that these enzymes are not identical.
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PMID:Vascular smooth muscle cells: a major source of the semicarbazide-sensitive amine oxidase of the rat aorta. 286 84

Cell fractions enriched in cardiac muscle cells (myocytes), on the one hand, and in non-myocytes, on the other, were prepared by dissociation of rat ventricular tissue with collagenase. Amine oxidase activities in homogenates of these cell fractions and also in homogenates of the corresponding undissociated ventricular tissue were compared. In addition, the activity of alkaline phosphatase (AP), an enzyme found predominantly associated in the heart with non-myocytes, particularly capillary endothelial cells, was also measured. No significant difference in the activity of MAO-A (assayed with 1 mM 5-hydroxytryptamine) was found between myocyte and non-myocyte fractions. In contrast, the activities of alkaline phosphatase (AP) and also the semicarbazide-sensitive amine oxidase (SSAO), assayed with 1 microM benzylamine (BZ), were both significantly higher in non-myocytes, by several-fold, than in myocyte fractions. Studies of the inhibition by clorgyline of 1 mM BZ metabolism confirmed that both MAO-A and MAO-B can also contribute to BZ oxidation in the rat heart. These experiments indicated different ratios of MAO-A: MAO-B in the various cell fractions. The ratios of the percentage contributions of MAO-A and MAO-B, respectively, to the total metabolism of 1 mM BZ were 78:20 (myocytes), 43:52 (non-myocytes) and 57:32 (undissociated tissue). These results suggest that MAO-B, in addition to AP and SSAO, may be associated preferentially with non-myocyte constituents of the rat heart. Although cardiac myocytes appear to contain predominantly MAO-A, this enzyme form is also localized, with high activity, to the non-myocyte fraction. However, since the non-myocyte fraction is heterogeneous in its cell content, containing vascular components of the coronary microcirculation, as well as other cells of connective tissue origin, the exact cellular localization of the enzyme activities within this fraction has not yet been defined.
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PMID:Monoamine oxidase activities of dissociated cell fractions from rat ventricular muscle. 646 72