Biomedical subjects

H K Parsadanian

Publications and source records attributed to H K Parsadanian.

5 recordsLinked to original sources

PubMed1989

Changes in the activity of enzymes, participating in glycogen metabolism of alloxan diabetic rats.

Alloxan diabetes induced in white rats by intraperitoneal injection of alloxan-monohydrate (15 mg/100 g body weight) was used to study changes in the glycogen phosphorylase a and b, phosphoprotein phosphatases and hexokinase activities under insulin deficiency conditions. Among the enzymes studied, an increase in muscle phosphorylase a activity as well as the a/b ratio have been obtained. In diabetic muscle phosphoprotein phosphatases and hexokinase activities were diminished. AMP increased the liver glycogen phosphorylase activity twice in diabetic rats whereas in normal animals the enzyme was less sensitive to this effector. The changes in liver hexokinase activity at diabetes were not connected and correlated with the altered phosphorylase and protein phosphatase activities. The logical chain of probable molecular events taking place in muscle glycogen metabolism under the conditions of insulin deficiency is offered.

Animals↗

PubMed1982

Multiple forms of phosphoprotein phosphatase and its protein inhibitors from rat brain.

By means of Sephadex A-50 ion exchange chromatography 5 peaks of phosphoprotein phosphatase (PPase) activity have been detected in rat brain. These molecular forms of the enzyme differ from each other by their specific activity as well as by a number of other properties--pH optima, heat and storage stability, and substrate specificity. It was shown that cyclic AMP (10(-5)-10(-6) M) decreased PPase activity of the majority of the peaks (I-III, V) and increased that of the peak IV. Ion exchange chromatography of brain tissue extracts revealed 4 peaks of PPase protein inhibitors. The results obtained on dialysis and tryptic digestion point to the protein nature of the inhibitors that differed from each other by their effect on the enzyme activity and heat stability (95 degrees C, 5 min). The significance of the specificity of separate molecular forms of PPases is discussed.

Animals↗

PubMed1977

Regulation of phosphorylase-phosphatase from skeletal muscle by phosphorylation of a regulator protein.

The inhibitory effect of a heat-stable regulator protein from skeletal muscle on the activity of phosphorylase-phosphatase (EC 3.1.3.17) was studied. The regulator protein was shown to be both phosphorylated and dephosphorylated in vivo as well as in vitro. The incorporation of phosphate into the regulator protein increased, while dephosphorylation decreased the ability of the protein to inhibit phosphatase activity. Our results suggest that the reversible phosphorylation of the regulator protein plays an essential role in the regulation of phosphorylase-phosphatase activity.

Animals↗

PubMedDate not supplied

Protein phosphatases: function and regulation.

Thousands of proteins are expressed in a typical mammalian cell, of which a third are now thought to contain covalently bound phosphate. About 200 protein kinases and 100 protein phosphatases have already been identified. Whereas the classification, properties and regulation of protein kinases are largely studied, the information about the protein phosphatase is far to be completed. Relatively better is studied a group of serine/treonine protein phosphatases. It has been discovered that besides the control of the key enzymes of metabolic pathways, these phosphatases participate in the regulation of gene transcription and cell division in eukariots. In addition, the identification of tyrosine protein phosphatases points to a novel intracellular signalling pathways, controlling cell-cell communication, cell proliferation and signal transduction of receptors for peptide hormones and growth factors. The recent progress in these families of protein phosphatases is the topic of present review.

Animals↗

PubMedDate not supplied

Vanadium as a factor that disturbs phosphorus metabolism in nervous tissue.

Vanadium and its derivatives are the well-known environmental pollutants. We obtained that ammonium vanadate suppressed the alkaline (AlP) and acid (AcP) phosphatases activity in the variety of tissues. Vanadate inhibited the enzymes that take part in phosphoryl transfer reactions. Successive concentration-dependent decrease in AlP and AcP activities by vanadate (0.1 mM-1 mM) has been obtained in rat nervous tissue. Moreover, the observed reduction in the sensitivity of the enzymes to vanadate ions becomes more pronounced at the transition from higher and relatively young regions of nervous system to its more ancient parts. Phosphoprotein phosphatase (PP) activity has also been inhibited in various structures of brain tissue; in spinal cord, however, vanadate in comparatively low concentrations (10 microM) caused a steep rise in the enzyme activity. Only at high concentration (1 mM) vanadate exert the effect of moderate inhibition. The possibility of the existence of phylogenetically different molecular forms of nervous tissue PPs differed by their sensitivity to vanadate was supported in our comparative examination.

Acid Phosphatase↗