Carbamates enzyme linkages

These devices are now being tested in demilitarization plants as monitors of stack exhaust atmospheres and work areas. We have not had the opportunity to determine the sensitivity of the devices to the numerous enzyme-inhibiting compounds which would be of interest to others. Generally, however, it is reasonable to expect, for instance, less sensitivity to P=S and P—S linkages and conversely better sensitivity to compounds where the sulfur is replaced by oxygen due to greater toxicity of these compounds. Such compounds as the carbamates, due to their inhibiting qualities, would also be expected to be detected with these systems. 

Traditionally in biochemistry (e.g. for affinity chromatography), enzymes have been covalently linked to carbohydrates such as agarose and dextran (Sepharose, Sephadex). The most widely used activation method is the cyanogen bromide (CNBr) method, yielding isourea and imidocarbonate functionalities that react with amines on the enzyme to produce N-substituted carbamate linkages. 

However, in 244, the enzyme is bound to the antibiotic via a carbamate functional group, which is much less reactive towards nucleophiles than a simple ester linkage. Some representatives of this class, e.g. 245,246 and 247, have been described [126-128,66,67], but there are no reports on their biological activity. 

Derbyshire et al. (1987) reported that an enzyme, isolated from the microoiganism Achromobacter sp., hydrolyzed carbofuran via the carbamate linkage forming 2,3-dihydro-2,2-dimethyl-7-benzofuranol. The optimum pH and temperature for the degradation of carbofuran and two other pesticides (aldicaib and caibaiyl) were 9.0-10.5 and 45 and 53°C, respectively. Degradation of caibofuran in poorly drained clay-muck, well drained clay-muck and poorly drained clay field test plots from British Columbia was veiy low. After 2 successive years of treatment, caibofuran concentiatioiis began to increase (Williams et al., 1976). 

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