Enzymes significance

While tractability for screening and ligand discovery has been demonstrated for these enzymes, significant challenges remain, notably in identifying chemotypes that show potent and selective inhibition of isoforms of interest while retaining physicochemical properties suitable for the intracellular site of action. 

PCB 156, a mixed inducer of microsomal enzymes, significantly increases the incidences of cleft palates by 2,3,7,8-TCDD in rodents (Bimbaum et al. 1985). Interactions among polychlorinated congeners may range from antagonism to additivity to synergism (Safe 1990), and the toxicity of individual PCBs can be raised by interaction with other PCBs (Table 24.5). 

Venlafaxine does not appear to inhibit cytochrome P450 enzymes significantly, and it is the antidepressant least likely to contribute to protein-binding interactions. Because of the risk of serotonin syndrome, venlafaxine should not be combined with MAOIs. 

The fate of intravenously administered hyaluronidase has been studied in humans and rats using 125I- or biotin-labeled hyaluronidase. The serum half-life in humans was approximately 3.2 minutes. Similar half-life values have been measured in rats. Within 10 minutes of administration the bulk of the enzyme accumulated in the liver (>50%) with measurable quantities in the kidneys and spleen. The presence of three high-mannose type oligosaccharide subunits per polypeptide chain probably accounts for the rapid uptake by the liver. Preadministration of mannans or deglycosylation of the enzyme significantly increased the serum half-life of hyaluronidase [106]. 

The second major problem in the interpretation of the kinetics of cerulo-plasmine catalyzed oxidations involves the unique role played by trace amounts of iron which contaminate the reaction mixtures. Curzon and O Reilly 161) observed that both Fe2+ and to a lesser extent Fe3+ at concentrations stoichiometric with enzyme significantly enhanced the oxidase activity of ceruloplasmin toward DPD, and they suggested that a number of the conflicting results in the literature were due to variations in the concentration of contaminating iron salts. Iron appears to be unique in this regard since Mn2+, Co2+, Ni +, and Zn2+ activated to no more than 50 % below 20 concentration while at higher concentrations the above divalent ions showed inhibition 148, 162). 

PCB 156, a mixed inducer of microsomal enzymes, significantly increases the incidences... 

The presence of CN and CO ligands of the active site Fe raises the question as to how these potentially toxic molecules are incorporated in the enzyme. Significant progress has been made in the elucidation of the biosynthetic pathway of cyanide from a carbamoyl phosphate precursor [61]. On the other hand, the origin of the CO ligand remains unclear [62]. Many proteins are involved in the biosynthesis and the maturation of the active site of [NiFe]-... 

Enzyme mimic A reacting molecule or system that shows at least some of the catalytic features of a ttue enzyme significant catalysis, substrate selectivity, enantioselectivity, turnover, etc. 

Safety The replacement of formerly aggressive conditions (high alkalinity, chlorine release) by enzymes significantly contributes to consumer safety [117]. Also, there is no risk of absorbing enzymes from dishes. During the cleaning process, they are widely denatured by pH and temperature, and no enzyme activity can be detected on the cleaned plates and dishes [13]. If trace amounts of enzymes were absorbed by the consumer upon use, the proteins would be denatured in the body as food proteins. 

Interstrain differences of TAT activity were obtained in mice after starvation. In C57BL/b mice, the activity of this enzyme significantly increased, whereas in DBA/2J mice it was lower than control levels (Blake, 1970). 

Lecithin cholesterol acyltransferase, LCAT, is the second enzyme of major importance in the enzymic phase of lipoprotein metabolism. Cholesteryl ester formation by this enzyme significantly changes the dynamics of the plasma cholesterol pool. Unlike the spontaneous rapid equilibration of cholesterol between lipoproteins. 

When producing maltose syrups, why does the addition of pullulanase or debranching enzyme significantly increase maltose content What are the major food uses of regular and high-maltose syrups ... 

---