Stimulated activating enzymes

Contraction of muscle follows an increase of Ca " in the muscle cell as a result of nerve stimulation. This initiates processes which cause the proteins myosin and actin to be drawn together making the cell shorter and thicker. The return of the Ca " to its storage site, the sarcoplasmic reticulum, by an active pump mechanism allows the contracted muscle to relax (27). Calcium ion, also a factor in the release of acetylcholine on stimulation of nerve cells, influences the permeabiUty of cell membranes activates enzymes, such as adenosine triphosphatase (ATPase), Hpase, and some proteolytic enzymes and facihtates intestinal absorption of vitamin B 2 [68-19-9] (28). 

Researchers at the MoneU Center (Philadelphia, Pennsylvania) are using a variety of electrophysical and biochemical techniques to characterize the ionic currents produced in taste and olfactory receptor cells by chemical stimuli. These studies are concerned with the identification and pharmacology of the active ion channels and mode of production. One of the techniques employed by the MoneU researchers is that of "patch clamp." This method aUows for the study of the electrical properties of smaU patches of the ceU membrane. The program at MoneU has determined that odors stimulate intraceUular enzymes to produce cycUc adenosine 3, 5 -monophosphate (cAMP). This production of cAMP promotes opening of the ion channel, aUowing cations to enter and excite the ceU. MoneU s future studies wiU focus on the connection of cAMP, and the production of the electrical response to the brain. The patch clamp technique also may be a method to study the specificity of receptor ceUs to different odors, as weU as the adaptation to prolonged stimulation (3). 

The interactions may be physicochemical without the participation of biological mechanisms for example, deep lung exposure to highly soluble irritative gases, such as sulfur dioxide, may become enhanced due to adsorption of the gas onto fine particles. Biological interactions may occur at all stages and body sites. For example, toxicity is increased when adverse effects are due to some reactive metabolic intermediate and exposure to another agent stimulates its metabolic activation (enzyme induction). 

For each of the following enzymes in A. rtiger, select metabolites from the list provided that either inhibit or stimulate activity during a) balanced growth and b) during dtric acid accumulation (caused by Mn2 defidency). 

A marked interference with heme synthesis results in a reduction of the hemoglobin concentration in blood. Decreased hemoglobin production, coupled with an increase in erythrocyte destruction, results in a hypochromic, normocytic anemia with associated reticulocytosis. Decreased hemoglobin and anemia have been observed in lead workers and in children with prolonged exposure at higher PbB levels than those noted as threshold levels for inhibition or stimulation of enzyme activities involved in heme synthesis (EPA 1986a). 

There are basically two different enzyme activities that can be stimulated in enzyme-linked receptors. A receptor tyrosine kinase recognizes one or more specific tyrosines in the target and uses ATP to phosphorylate it. Often part of the activation involves the receptor phosphoryla-... 

Exposure of various invertebrate species to high concentrations of petroleum did not induce mixed function oxidase activity. Enzyme activity was stimulated, however, in a number of fish tissues by petroleum. Different permutations can be addressed as to the significance of basal or induced levels of mixed function oxidases and hydrocarbon toxicity. AHH may have a physiological role in enhancing hydrocarbon clearance but may also increase the mutagenic-carcinogenic potential of hydrocarbons. Both of these concepts have been demonstrated in studies with fish (29,30). Induced AHH levels may permit a more rapid oxidative transformation with concomitant "disappearance" of parent hydrocarbons, but potentially toxic metabolites could be retained in tissues for longer periods (31). It is likely that at the enzymic level the... 

Human Set9 is a 50 kDa H3 methyltransferase that methylates Lys-4 of H3. The enzyme methylated free H3 but not H3 in chromatin substrates. There is evidence that Set9 may stimulate activated transcription [198]. Set9 has the SET domain but lacks the cysteine-rich (pre-SET and post-SET) domains. Disruption of Saccharomyces cerevisiae and Saccharomyces pombe Setl obliterates H3 methyl Lys-4 [199]. Thus this SET domain containing protein appears to be a H3 Lys-4 methyltransferase, catalyzing both di- and tri-methylation of H3 Lys-4 [155]. However, studies with recombinant Setl failed to show histone methyltransferase activity. It has been suggested that other associated proteins may be required for the Setl to be catalytically active [139,200]. Indeed, Setl is associated with several... 

The properties of bilirubin UDP-glucosyl- and bilirubin UDP-xylosyl-transferase from rat liver closely parallel each other with regard to activation by digitonin and dependence on pH and bivalent metal ions. Considerable fractions of the enzyme activities (especially of the glucosyl-transferase) functioned independently of added bivalent cation (F3). The observations are compatible with identical enzyme locations, at least for the metal ion-stimulated activities. 

The main effect of efferent action of Hepamal preparation is inhibition of LPO processes, increase of antioxidative abiUty of the organism and stimulation of enzymes of the organism s detoxication system. These activities are stipulated by natural vitamin complexes (A, E, PP, C, 6-carotenes, foUc acid) present in Hepamal, which have high antioxidative potential, whereas flavonoids and terpenoids, also present in the preparation, stimulate both detoxication phases. 

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