Enzyme Conversion

Binders. Paper-coating biaders are either polymers derived from aatural sources or syathetic polymers. The largest volume, aaturally derived biader is starch (qv) (99). Starch is provided ia derivatized form or unmodified form pead com starch is used predomiaanfly for the latter. Unmodified starch is solubilized by thermal conversion or enzyme conversion. The most common derivatized products are acetylated [9045-28-7] oxidized, and hydroxyethylated starches. 

P-amylase, and debranching enzymes. Conversion of D-glucose to D-fmctose is mediated by glucose isomerase, mosdy in its immobilized form in columns. Enzymic degradation of starch to symps has been well reviewed (116—118), and enzymic isomerization, especially by immobilized glucose isomerase, has been fiiUy described (119) (see Syrups). 

More than 30 years ago Jacob and Monod introduced the Escherichia coli lac operon as a model for gene regulation. The lac repressor molecule functions as a switch, regulated by inducer molecules, which controls the synthesis of enzymes necessary for E. coli to use lactose as an energy source. In the absence of lactose the repressor binds tightly to the operator DNA preventing the synthesis of these enzymes. Conversely when lactose is present, the repressor dissociates from the operator, allowing transcription of the operon. 

A homogeneous electrochemical enzyme immunoassay for 2,4-dinitrophenol-aminocaproic acid (DNP-ACA), has been developed based on antibody inhibition of enzyme conversion from the apo- to the holo- form Apoglucose oxidase was used as the enzyme label. This enzyme is inactive until binding of flavin adenine dinucleotide (FAD) to form the holoenzyme which is active. Hydrogen peroxide is the enzymatic product which is detected electrochemically. Because antibody bound apoenzyme cannot bind FAD, the production of HjOj is a measure of the concentration of free DNP-ACA in the sample. 

Multiple-enzyme conversion of CO2 to formate, then formaldehyde, then methanol by FateDH, FaldDH, and ADH Enzymes loaded in CaC03 followed by LbL deposition and dissolution of core, then encapsulation into a gel bead... 

The tabulated data of initial rates and concentrations were obtained for enzyme conversion of a substrate at 37 C, pH 6.5. 

Oxidation of purine derivative, oxidation of allopurinol to alloxanthene FAD dependent oxidative deamination of monoamines, e.g. primaquine Pyridoxal dependent, copper containing enzyme. Conversion of allylamine to acrolein... 

The Reactions and the Enzymes Conversions with Nitriie Hydratase and Amidase Concluding Remarks... 

This enzymic conversion involves two enzymes, a dehydrogenase and an isomerase. The dehydrogenase component oxidizes the hydroxyl group on pregnenolone to a ketone, and requires the oxidizing agent cofactor NAD+ (see Box 11.2). The isomerase then carries out two tautomerism reactions, enolization to a dienol followed by production of the more stable conjugated ketone. 

A. Webster et al. (41) showed that enzymes could be used to convert synthetic H203P—CH2—CH2—CHOH—COOH, the analogue of 3-phosphoglycerate, into the corresponding phosphonomethyl analogue of fructose 6-phosphate (Fig. 2), which they isolated. They obtained evidence for the enzymic conversion of this into the analogue of glucose... 

Srivenugopal, K.S. Adiga, P.R. Enzymic conversion of agmatine to putrescine in Lathyrus sativus seedlings. J. Biol. Chem., 256, 9532-9541 (1961)... 

Secondary alicyclic amines, such as pyrrolidine and piperidine, have many properties typical of the corresponding aliphatic amines. Metabolic oxidation at secondary alicyclic nitrogens results in the formation of hydroxylamines, which may then undergo enzymic or non-enzymic conversion to nitrones, and in some cases to nitroxide radicals. For example, the 2-substituted piperidino derivative (- )-anabasine (1), a tobacco alkaloid, is metabolized initially to a hydroxylamine (2) and then to the nitrone (3), when incubated with liver and... 

FOS and oligofuctose are fructose oligomers that are either produced by enzymic conversion of sugar or extracted from chicory, as inulin, and then hydrolysed. These products behave as soluble fibres and prebiotics. In acid conditions, they can hydrolyse, but are usually sufficiently stable for short-shelf-life juices, near-water products with low acid levels or powdered soft drinks. Prebiotic activity varies with preparation and required daily dose can be as low as 2.5-5.0 g/day for shorter chain FOS preparations (DP 2 1). Some positive effects on magnesium absorption and calcium absorption (in some populations) have also been shown (Beghin Meiji, 2001). 

We finish this Section with enzymic conversions that are difficult to classify elsewhere Takasweet, a commercial variety of immobilized glucose-iso-merase, converts 6-O-methyl-D-fructose and 6-deoxy-D-fructose into the gluco isomers in not very satisfactory yield.34 A mixture of catalase (75 U/mmol) and glucose oxidase (80 U/mmol) oxidizes xylitol to L-xylose in 50% yield, on the 100- mol scale.106 The enzyme cyclodextrin a-(l—>4)-glucosyltransferase (1000 U immobilized on silica gel-glutaraldehyde) allows107 preparation of cyclomaltohexaose (0.3 g), cyclomaltoheptaose... 

Tjlood coagulation is preceded by a sequence of zymogen-to-enzyme " conversions brought about by some very specific proteases (i). In these processes the interaction between coagulation factors and phospholipids plays a crucial role (2) by accelerating some of the reaction steps leading to clot formation. 

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