Inhibition of phytohemagglutinin-stimulated lymphocyte transformation by neutral SH-dependent proteinase of the spleen

The effect of neutral SH-dependent proteinase of the spleen on transformation of human peripheral blood lymphocytes has been studied. Proteinase (1--10 micrograms/ml) inhibits phytohemagglutinin-stimulated (PHA) lymphocyte transformation and has no effect on spontaneous transformation. Proteinase does not alter the mitogenic properties of PHA and possesses no cytotoxicity. Therefore, inhibition of stimulated lymphocyte transformation is either resultant of proteinase direct action on the cell or associated with the inhibitor factor formation.     

Increased substrate selectivity during transition from Ca2+-activated to K+,EDTA-activated nucleoside triphosphatase activity of heavy meromyosin

A comparison of kinetic parameters (Km(app) and V) of hydrolysis by heavy meromyosin of natural (ATP and ITP) and modified nucleoside triphosphates showed that in the K+, EDTA-ATPase conformation the enzyme exhibited a higher selectivity towards the structure of the substrate nucleoside moiety than in the case of the Ca2+-stimulated nucleoside triphosphatase activity. In the presence of Ca2+, all the N1- and N6-substituted analogs of ATP as well as ITP, etheno-ATP and the dialdehyde derivative of ATP were hydrolyzed at a high rate irrespective of their markedly decreased affinity for heavy meromyosin. In the presence of K+, EDTA the ATPase activity showed a tendency for a total decrease of the analog affinity for nucleoside triphosphates, i.e., the impossibility of tight binding of the substrate phosphate residues to the protein in the absence of bivalent cations, which was concomitant with an increase in the hydrolysis rate. However, it was found that only in N1-substituted analogs any appreciable changes in the substrate properties were absent. All the other nucleoside triphosphates tested (N6-carboxy-methoxy-ATP, N6-(N'-acetylaminoethoxy)-ATP, etheno-ATP, ITP and the dialdehyde derivative of ATP having a rupture in the ribose ring) lost their ability to be hydrolyzed by heavy meromyosin. The experimental results as well as the literature data are suggestive of differences in the spatial structure of the active center in two different myosin conformations associated with a high catalytic activity, i.e., K+, EDTA-ATPase and Ca2+-ATPase.     

Antimicrobial action spectrum of triterpene and steroid glycosides]

Antimicrobial activity of 9 triterpene glycosides of the plant and animal origin was studied. It was found that saponins inhibited the fungal growth to different extents and had no activity against grampositive and gramnegative bacteria. Triterpene glycosides of the animal origin, i.e. holoturins A and B, stichoposids A and C had the most pronounced antifungal activity as compared to the saponins isolated from plants. Changes in the length of the carbon chain from 2 to 6 monosugars had no significant effect on the activity of the triterpeneglycosides studied.