Inhibition by chelating agents

Inhibition by chelating agents has been reported only in the case of the Zn2+-dependent /1-lactamase II (47,106). Alcohols may inhibit (107), or stimulate (102). The inhibitory effect of alkyl sulfates (108,109) depends on the length of the alkyl chain (109, 110). 

The rate of incorporation of cupric ions into protoporphyrin dimethyl ester was found to be accelerated by a factor of ca. 20,000 in the presence of aqueous micellar sodium dodecyl sulfate (2-5%) relative to that in 5% CTAB (Lowe and Phillips, 1961). This rate acceleration was found to be the consequence of a change in the activation entropy and was attributed to micellar solubilization of the porphyrin ester such that the pyrrole nitrogen atoms are located in the Stern layer in close proximity to cupric ions electrostatically attracted to the anionic micellar surface. The rate of incorporation of cupric ions in the presence of NaLS was also found to be catalyzed and inhibited by chelating agents (Lowe and Phillips, 1961, 1962). 

Enzymes that are dependent on divalent metal ion (e.g., Mg " " and Ca " ") for activity are inhibited by chelating agents (e.g., ethylenediamine tetraacetate) that remove the metal ion from the enzyme. 

Potassium linolenate is reported to be readily oxidised in the presence of barbituric acid or thymine uracil and uric acid, however, were found to be anti-oxidants. The pro-oxidant effects of barbituric acid were inhibited by chelating agents [134]. 

A few facts are also known concerning the metabolism of alkanes by plants. Cuticular waxes typically contain secondary alcohols, ketones and ) -diketones in addition to alkanes and the former have the skeletons as in Figure 8, where functionalization is near the centre of the molecule and the chain lengths of the alcohols and ketones are closely similar to those of the major n-alkanes present in any particular species. Tracer evidence indicates that the secondary alcohol and ketone are formed in sequence by oxidation of the corresponding n-alkane by a mixed function oxidase which is inhibited by chelating agents. Thus in Brassica species, the 14- or 15-hydroxy- and oxo-derivatives of the n-C29 alkane were thus formed both in vivo and in cell-free extracts ". ... 

In addition to pyridoxal phosphate it has been reported that 5HTP decarboxylase also seems to require a metal. This metal requirement stems from the finding that chelating agents such as ethylenediamine tetraacetate inhibit activity (Beiler and Martin, 1954). Inhibition by chelating agents has been confirmed in the reviewer s laboratory. 

Table 2. Inhibition by chelating agent and trypsin inactivation of activated cysteine dioxygenase...

Comments Acts on phosphorus anhydride bonds (such as phosphorus-halide and phosphorus-cyanide) in organophosphorus compoimds (including "nerve gases"). Inhibited by chelating agents requires divalent cations. Related to EC 3.1.8.1 aryldialkylphosphatase. Previously listed as EC 3.8.2.I. 

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