Deamination, enzymic

Such interference falls into two classes competitive substrates and substances that either aaivate or inhibit the enzyme. With some enzymes, such as urease, the only substrate that reacts at reasonable rate is urease hence, the urease-coated electrode is specific for use (59, 165). Likewise, uricase acts almost specifically on uric acid (167), and aspartase on aspartic acid (8, 168). Others, such as penicillinase and amino oxidase, are less specific (63,169,170). Alcohol oxidase responds to methanol, ethanol, and allyl alcohol (171, 172). Hence, in using electrodes of these enzymes, the analyte must be separated if two or more are present (172). Assaying L-amino acids by using either the decarboxylative or the deaminating enzymes, each of which acts specifically on a different amino... 

Santaniello, E., Ciuffeda, P. and Alessandrini, L. (2007) Deaminating enzymes of the purine cyde as biocatalysts for chemoenzymatic synthesis and transformations of antiviral agents structurally related to purine nucleosides, in Biocatalysis in the Pharmaceutical and Biotechnology Industries (ed. R. Patel), CRC Press, Chapter 17. 

Gebauer, C.R. Rechnitz, G.A. Deaminating enzyme labels for potentiometric enzyme immunoassay. Anal. Biochem. 1982, 124, 338-348. 

Urease (urea amidohydrolase, EC 3.5.1.5) has the advantage that in the presence of the pH indicator bromocresol purple it produces a sharp unequivocal endpoint with its substrate, urea (Chandler et al, 1982). Moreover, it is absent from mammalian cells. Though urease can also be used for potentiometric EIA (Section 14.6.5), other deaminating enzymes, in particular asparaginase (Gebauer and Rechnitz, 1982), are more promising. The major drawback of urease is the possibility of rapid loss of enzyme activity. Type VII or C-3 urease (Sigma) from Jack beans [Canavalia ensiformis) are the most frequently used enzyme preparations. The physicochemical properties of urease are compiled in Table 10.14. 

The last fiber-optic biosensor to be presented is based on the immobilization of a deaminating enzyme at the sensing tip of a fiberoptic ammonia probe. Figure 11 shows the various membrane phases involved in the response of the ammonia probe. The key phase is the indicator solution which contains a pH indicator dye and ammonium chloride. The indicator solution is separated from the sample by a... 

S-mono-oxygenase and the reduced enzyme requires the presence of additional reductant for hydroxylase activity. The deaminating enzyme benzylamine oxidase consists of two subunits and has two tightly bound, but well separated,... 

Oxidative deamination, however, is a well-established process. It can be brought about by the action of hydrogen peroxide, or by deaminating enzymes (amino acid dehydrogenases) present in certain tissues, and the resulting keto acids have been isolated and identified (Krebs, Bernheim). 

Deaminating enzymes occur in kidney cortex and, to a lesser extent, in liver. Vertebrate intestinal mucosa and cardiac muscle of pigeons and frogs have a slight and restricted capacity for deamination. Other vertebrate tissues (brain, retina, spleen, bone-marrow, pancreas, salivary gland and mammalian heart) appear to be incapable of deaminating amino acids. The ammonia released in deamination is either transformed locally in the liver into urea, or is transported to the liver by an ammonia carrier for conversion into mea. A small part of the renal ammonia escapes into the urine, and serves to regulate its H-ion concentration. 

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