The nitrile hydratase from Rhodococcus equi A4 consisted of two kinds of subunits which slightly differed in molecular weight (both approximately 25 kDa) and showed a significant similarity in the N-terminal amino acid sequences to those of the nitrile hydratase from Rhodococcus sp. N-774. The enzyme preferentially hydrated the S-isomers of racemic 2-(2-, 4-methoxyphenyl)propionitrile, 2-(4-chlorophenyl)propionitrile and 2-(6-methoxynaphthyl)propionitrile (naproxennitrile) with E-values of 5-15. The enzyme functioned in the presence of 5-98% (v/v) of different hydrocarbons, alcohols or diisopropyl ether. The addition of 5% (v/v) of n-hexane, n-heptane, isooctane, n-hexadecane, pristane and methanol increased the E-value for the enzymatic hydration of 2-(6-methoxynaphthyl)propionitrile.

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Short incubation (1 -5 h) of aromatic dinitriles with resting cells of Rhodococcus equi A4 produces the correspondin.~ cyano amides in 48 -81% yield. The substrate reactivity decreases m order 1,4-> 1,3± > 1,2-dlsubstitution. Prolonged ~eatment (20 -50 h) is needed to achieve the conversion to acid or for transformation of the second cyano group.