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H Kunze

Publications and source records attributed to H Kunze.

At least 37 records · Page 2Linked to original sources
PubMed1992

Annexin II inhibits calcium-dependent phospholipase A1 and lysophospholipase but not triacyl glycerol lipase activities of rat liver hepatic lipase.

A member of the annexin family (the heterotetrameric annexin II2p11(2) complex purified from porcine intestinal epithelium) was tested for its ability to affect different calcium-dependent intrinsic lipolytic activities of rat liver hepatic lipase (HL). Whereas annexin II in the presence of calcium failed to interfere with HL triacyl glycerol lipase (EC 3.1.1.3) activity, it inhibited HL phospholipase A1 (EC 3.1.1.32) and lysophospholipase (EC 3.1.1.5) activities. Inhibition could be overcome by increasing the substrate concentration. Under phospholipase A1 assay conditions, annexin II did not bind to the purified HL enzyme. These results therefore suggest that only inhibitor/substrate interactions lead to inhibition of HL phospholipase A1 and lysophospholipase activities, an obviously general mechanism of phospholipase inhibition by annexins. Possible implications of HL inhibition in vivo by annexins are discussed.

Animals↗
PubMed1992

Implication of acid cholesteryl ester hydrolase in the regulation of steroid biosynthesis in rat Leydig cells.

Cholesteryl ester hydrolase (CEH) activities with different pH optima, i.e. at about pH 4.0 and pH 7.0, were found in Leydig cells isolated from rat testis. Highly purified intact Leydig cells responded to human chorionic gonadotropin treatment with increased intracellular cAMP levels, increased testosterone release, and a 1.5-fold stimulation of the acid CEH activity. Treatment of non-stimulated homogenised cells with cAMP-dependent proteinkinase, cAMP and ATP lead to a 3.0-fold stimulation of the acid CEH activity. These findings suggest that interconvertible CEH with an acidic pH optimum--presumably of lysosomal location--contributes to the regulation of steroidogenesis in Leydig cells.

Animals↗
PubMed1991

Partial characterisation and subcellular distribution patterns of endothelin-1, -2 and -3 binding sites in human liver.

For the first time, endothelin-1, -2 and -3 (ET-1, -2, -3) binding sites were characterized in human liver and shown to differ significantly in their respective dissociation constants and densities. In addition, subcellular distribution patterns of these binding sites in biochemically analysed fractions obtained after differential centrifugation were shown to be heterogeneous. Thus, the bulk of ET-1 and ET-3 binding sites seemed to be present in plasma membranes, although their partial presence in a compartment sedimenting together with the endoplasmic reticulum cannot be excluded. In contrast, a major proportion of the ET-2 binding sites appeared to be associated with a compartment sedimenting together with mitochondria, suggesting a special accumulation of ET-2 binding sites in human liver. A significant portion of ET-1, -2 and -3 binding sites seems to be localized also in lysosomes, presumably indicating their participation in the internalisation process.

Binding Sites↗
PubMed1991

Elemental composition of airborne dust in the Shale Shaker House during an offshore drilling operation.

During 2 days of an offshore drilling operation in the North Sea, 16 airborne dust samples from the atmosphere of the Shale Shaker House were collected onto filters. During this operation, drilling mud composed of a water slurry of barite (BaSO4) together with minor amounts of additives, among them chrome lignosulphonate and chrome lignite, was circulated between the borehole and the Shale Shaker House. The concentration of airborne dust in the atmosphere was determined and the elemental composition of the particles analysed by both PIXE (proton-induced X-ray emission) and ICP-MS (inductively coupled plasma-mass spectrometry). The total amount of dust collected varied from 0.04 to 1.41 mg m-3 with barium (Ba) as the single most abundant element. The open shale shakers turned out to be the major cause of generation of dust from the solid components of the drilling mud.

Air Pollutants, Occupational↗
PubMed1991

Improved procedure for the purification of hepatic lipase from rat liver homogenate.

A procedure is described for the purification of hepatic lipase (HL)4 from rat liver homogenate which results in a high yield (41%) of electrophoretically homogeneous enzyme. The method is based on that of Twu et al. (Biochim. Biophys. Acta 1984: 792, 330), but it is more efficient with respect to yield (about 4-fold) and purity (1.6-fold). It includes the preparation of a high-speed supernatant, chromatography in series on octyl-, heparin- and concanavalin A-Sepharose, and finally gel filtration. On SDS-PAGE analysis, the purified enzyme exhibited an apparent molecular mass of 63.6 +/- 3.2 kDa. Heterogeneity was observed, when purified HL was subjected to isoelectric focussing. The enzyme displayed a specific catalytic activity of 23,000 U* (mumol fatty acid released per h at 37 degrees C) per mg protein, when assayed with trioleoyl glycerol suspensions in arabic gum. A highly specific antiserum against rat liver HL, capable of inhibiting 817 mU* HL per microliter antiserum, was raised in rabbits.

Animals↗
PubMed1990

Protease inhibitors reduce lysosomal acid phospholipase A1 activity in cultured rat hepatocytes.

When rat hepatocytes were cultured in the presence of various specific protease inhibitors, lysosomal acid phospholipase A1 activity decreased progressively. Exposure of the cultured cells to 0.1 micrograms/ml of pepstatin, E 64, leupeptin or chymostatin also reduced the catalytic activities of several lysosomal marker enzymes. Irrespective of the protease inhibitor type employed, acid phospholipase A1 activity reacted most sensitively, followed by acid phosphatase, acid beta-N-acetyl-D-hexosaminidase and acid beta-glucuronidase. Of the protease inhibitors studied, pepstatin appeared to be most potent in reducing lysosomal enzyme activities in cultured hepatocytes. These findings suggest that proteolytic processes at as yet unknown, possibly extralysosomal sites play an important role in the turnover rates of lysosomal enzymes.

Animals↗
PubMed1989

Biospecific dye-binding and hydrophobic interaction chromatography as tools for high yield preparation of purified phospholipase A1 from rat liver.

A basically new approach is presented for purifying lysosomal phospholipase A1 (EC 3.1.1.32) from rat liver. This procedure not only simplifies and speeds up the purification process, but also improves the yield in comparison to the most efficient methods reported so far. A high recovery of about 88% was achieved by (1) homogenisation of whole rat liver in a hypotonic medium, (2) acid precipitation, (3) combined dye binding chromatography on triacinyl dyes (Yellow H-A and Red HE-3B) immobilised to agaroses, and (4) combined concanavalin A-Sepharose and phenyl-Sepharose chromatography. Ethylene glycol was required for enzyme stabilisation as well as for enzyme elution in dye-binding and hydrophobic chromatography. In SDS-polyacrylamide slab gel electrophoresis, the purified material showed two major protein bands of 56 and 33 kDa, which amounted to about 85 and 12%, respectively, of the total protein visualised. Under reductive conditions, the 56 kDa protein decomposed completely into three subunits of 30, 21 and 20 kDa. The 33 kDa protein in the non-reduced material seems to be identical with the 30 kDa protein in the reduced material. Native polyacrylamide gel electrophoresis provided strong evidence that the 56 kDa protein is the active form of PLA1. The purified material displayed a specific activity of approximately 7.7 mumol fatty acid released per min per mg of protein using 200 microM phosphatidylethanolamine as a substrate.

Animals↗