Biomedical subjects

B Wiederanders

Publications and source records attributed to B Wiederanders.

86 records · Page 5Linked to original sources

PubMed1977

Cathepsin H: an endoaminopeptidase from rat liver lysosomes.

1. Cathepsin H is an endoaminopeptidase belonging to the group of thiol enzymes. It was purified from rat liver lysosomes by gel filtration on Sephadex G-75, chromatography on CM-Sephadex C-50, on DEAE-Cellulose DE-52 and subsequently on an organomercurial absorbent. 2. The molecular weight of cathepsin H was found to be 28,000 and the isoelectric point was estimated to be at pH 7.1 by analytical isoelectric focusing. 3. Cathepsin H has to be designated as endoaminopeptidase, because it catalyzes the hydrolysis of proteins, N-terminal substituted proteins and amino acid derivatives, respectively, as well as of peptides of various chain length and N-terminal free amino acid derivatives. Cathepsin H shows amidase and esterase activity, but it does not show carboxypeptidase activity. The finding of the amino- and endopeptidase nature of cathepsin H has been revealed mainly by the results obtained with inhibitors and by the rather high temperature stability of the enzyme. The chlormethyl ketone of leucine proves to be the strongest inhibitor of the aminopeptidase as well as of the endopeptidase activity, whereas leupeptin endopeptidase activity and endopeptidase substrates inhibit competitively the aminopeptidase activity. 5. Cathepsin H shows highest activity at pH 6.0 in the presence of 1--5 mM GSH and EDTA. 6. The enzyme is stable for several months at slightly acid pH values in a deep frozen state.

Animals↗

PubMed1976

[On the age dependence of the intracellular proteolysis (author's transl)].

We report the age dependent changes of the proteolytic capacity of the rat liver at pH 3.0 and pH 6.0. The total proteolytic activity increases during the whole cycle. During the weanling period the specific activity (mug substrate split x min-1 X mg liver protein-1) rises up to values about 30% higher than those of the remaining lifetime. We found the specific activity in old male animals (18 months) to be lower than in younger ones (5 months). These findings are correct for the liver homogenate as well as for the cell fractions.

Aging↗

PubMed1976

[Intracellular protein breakdown. VIII. The use of double-labeled proteins as substrates].

Double-labeled proteins from rat liver cytosol (14C in long-lived, 3H in short-lived proteins after in-vivo-labeling) are used as substrates for unlabeled proteinases in vitro. Differences in the degradation rates of short-lived and long-lived proteins in vitro by different proteinases and after addition of different effectors allow conclusions concerning their importance for the in-vivo-turnover of substrate proteins. The main activity (greater than 90%) of soluble-lysosomal proteinases at pH 6,1 and pH 6,9 is caused by thiolproteinases, which degrade preferentially short-lived cytosol proteins. These proteinases are inhibited by leupeptin. Autolysis of double-labeled cell fractions shows a remarkably faster breakdown of short-lived substrate proteins only in the soluble part of lysosomes. Microsomal fractions degrade in vitro preferentially long-lived substrate proteins.

Animals↗

PubMed1976

[Intracellular protein breakdown. VI. Isolation, properties and biological significance of cathepsin D from rat liver].

The preparation and properties of cathepsin D from rat liver are reported. The enzyme is an endopeptidase of lysosomal origin. The molecular weight was estimated to be 49000 by sodium-dodecylsulfate electrophoresis. We did not find any dissociation into subunits under reducing conditions, in contrast to some other authors. We found the enzyme to occur in at least 4 forms with the isoelectric points 5.87, 5.65, 5.41 and 5.13. Strong -SH-blocking reagents inhibit the activity, but the most powerful and specific inhibitor was pepstatin (Ki=38 nM). The substrate specificity is discussed. There was no proof for any zymogen activation in a great number of experiments. Since the cathepsins B1, B3 and L obviously seem to play the major role in the intracellular protein breakdown within the rat liver, the main task of cathepsin D is the degradation of extracellular proteins in this organ.

Animals↗

PubMed1976

[Intracellular protein breakdown. VII. Cathepsin L and H; two new proteinases from rat liver lysosomes].

Some properties (molecular weight, pI, temperature stability, action of selected inhibitors, substrate specificity and pH-activity dependence) of two not yet known cathepsins from rat liver lysosomes are compared with the properties of the known cathepsin B1. Cathepsin L is a thiolproteinase, has a molecular weight of 23--24000 and a pI of 5,8--6,1. By disc electrophoresis and isoelectric focusing there appear several protein bands which all have enzymatic activity. Leupeptin behaves as a strong inhibitor. The pH-optimum for digestion of proteins is close to 5,0. Cathepsin L does not hydrolyse esters and splits synthetic low molecular substrates only to a low degree. Cathepsin L stored in presence of glutathion and EDTA in liquid nitrogen kept its activity for some months. Cathepsin H is an aminopeptidase as well as an endopeptidase. An enzyme with these bifunctional properties was detected up to now only in E. coli but not in animal cells. Cathepsin H is a thiol-enzyme with a molecular weight of 28000 and a pI of 7,1. Strong inhibitors are leucyl-chlormethan and SH-blocking substances. Leupeptin shows only a weak inhibitory effect to this enzyme compared to its action on cathepsins L and B1. The pH-optimum for hydrolysis of all substrates is 6.0. Cathepsin H splits proteins, amino acid derivatives and selected N-protected amino acid derivatives. Cathepsin H compared to cathepsin L and B1 is quite temperature stable.

Animals↗

PubMed1975