[Insulin-degrading neutral protease from plasma membranes of rat liver cells and erythrocytes]. / Insulinrasshchepliaiushchaia neitral'naia proteinaza plazmaticheskikh membran kletok pecheni i éritrotsitov krys.

Insulin-degrading neutral proteinase with molecular weight of 70 kDa was partly purified from the rat liver and erythrocyte plasma membranes. Incubation of membranes with [gamma-32P]ATP resulted in the enzyme phosphorylation. Intensity of this process greatly increased in the presence of insulin (100 microU/ml), and correlated with the elevation of the insulin-degrading activity in proteinase. Ca2+, Mn2+, dithiothreitol, cysteine were shown to have a stimulatory effect on insulin degradation; p-chloromercuribenzoate significantly repressed this process. Phenylmethylsulphonyl fluoride and soybean trypsin inhibitor did not affect the activity of the proteinase. It was concluded that the investigated enzyme was a calpain and may participate in the mechanism of insulin action.

[Insulin-degrading neutral proteinases of the plasma membrane of loach liver and embryo cells]. / Neitral'nye proteinazy plazmaticheskikh membran kletok pecheni i zarodyshei v'iuna, rasshchepliaiushchie insulin.

Insulin-degrading, Ca2+-activated, neutral proteinases of molecular weight about 150 kDa and 70 kDa were purified from plasma membranes of the loach liver and embryo cells. It was shown that dithiothreitol and cysteine enhanced the enzyme activity, whereas p-chloromercuribenzoate and iodoacetic acid inhibited its level. Incubation of isolated plasma membranes with 5'[gamma 32P]ATP resulted in phosphorylation of these proteinases. The intensity of the process increased under the influence of insulin (100 microU/ml), that correlated with a decrease in the activity of proteinase with molecular weight of 150 kDa and an increase in 70 kDa enzyme activity. The data suggest the existence of common regulatory pathways of insulin degradation in plasma membranes of the loach liver and embryo cells.

[Proteolysis in the cells of malignant human and animal tumors]. / Proteoliz v kletkakh zlokachestvennykh opukholei cheloveka i zhivotnykh.

The data concerning proteolytic enzymes in human and animal malignant tumours are reviewed. The activity of these proteinases, its changes in the course of the disease, intracellular localization and secretion into the extracellular space and blood are discussed. The role of proteolytic enzymes including the role of plasminogen activator in tumour progress and during the metastasis development is considered.

[Properties of cathepsin D from unfertilized eggs, embryos and skeletal muscles of the loach]. / Svoistva katepsina D neoplodotvorennykh iaitsekletok, zarodyshei i skeletnykh myshtsv'iuna.

The action and some properties of cathepsin D, partly purified from unfertilized loach eggs, embryos and skeletal muscles were determined. The enzyme from embryo cells displays the activity maximum at pH 3.0 and pH 4.8 while enzyme from skeletal muscles--only at pH 3.0. Cathepsin D purified from all three sources splits actively hemoglobin, albumin, alpha-glycerophosphate dehydrogenase, pyruvate kinase and practically does not influence casein, hexokinase, glucose-6-phosphate dehydrogenase. The enzyme is comparatively thermolabile and its activity decreases in the presence of thiol compounds. The main part of cathepsin D in skeletal muscle cells and in embryo cells is precipitated after differential centrifugation of homogenates (25000 g; 60 min).