Enzyme desulfinase

In the fourth and final step, the intermediate 2-(2,-hydroxyphenyl)ethen-l-sulfmate (HPESi ) is desulfinated to 2-(2 -hydroxyphenyl)ethan 1-al (HPEal). As seen from Fig. 4, this step cannot be catalyzed by the arylsulfinate desulfinase like DszB. Instead, the enzyme has to be an alkenylsulfmate desulfinase. The alkenyl C-S bond as present in the intermediate, can only be desulfurized by hydroxylase-type enzyme, giving an enol, which can then tautomerize to HPEal and sulfite. However, the identity of the sulfur-containing product has not been confirmed [34],... 

The desulfinase enzyme from R. erythropolis IGTS8 and R. erythropolis KA2-5-1 have been isolated and characterized [55,126,163,164] however, the latter enzyme had to be cloned into E. coli, to obtain sufficient enzyme for characterization. Both enzymes have an optimum activity at a temperature of 35°C, but slightly different pH optimum (Table 7). The Km values for HBPSi for the two enzymes were similar but the kcat values were different, probably due to the use of different assays to assess enzyme activity. The fccat values for the IGTS8 enzyme did match closely with that reported by the Gray study [53], Expression of the KA2-5-1 enzyme in E. coli required co-expression of chaperonin genes, groEL/groES. 

Table 7. Properties of the desulfinase enzyme from different strains R. erythropolis IGTS8, R. erythropolis KA2-5-1, and Paenibacillus sp. All-2...

The desulfinase enzyme was reported to have narrow substrate specificity. In addition to HBPSi, only 2-phenyl benzene sulfinate was reported to serve as a substrate [164], It was found to be inactive against benzene sulfinate, cysteine sulfinate, benzene sulfonate, /7-toluene sulfonate, 1-octane sulfonate, methane sulfonate, and taurine. This enzyme was found to be inhibited by HBP beginning at 0.5 mM with complete loss of activity at 9 mM HBP, but was not affected by sulfite. 

Nakayama, N. Matsubara, T. Ohshiro, T., et al., A Novel Enzyme, 2 -Hydroxybiphenyl-2-Sulfinate Desulfinase (DszB), From a Dibenzothiophene-Desulfurizing Bacterium Rhodococcus Erythropolis KA2-5-1 Gene Overexpression and Enzyme Characterization. Biochimica Et Biophysica Acta-Proteins and Proteomics, 2002. 1598(1-2) pp. 122-130. 

This enzyme [EC 4.1.1.12], also known as desulfinase, catalyzes the conversion of aspartate to alanine and carbon dioxide. Pyridoxal phosphate is a required cofactor. The enzyme will also catalyze the decarboxylation of aminomalonate as well as the desulfination of 3-sulfino-alanine to sulfite and alanine. 

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