Catalytic properties of aminoacylase of strain Rhodococcus armeniensis AM6.1

Abstract

Studies of substrate specificity revealed that the D-aminoacylase of Rhodococcus armeniensis AM6.1 strain exhibits absolute stereospecificity to the D-stereoisomers of N-acetyl-amino acids. The enzyme is the most active reacted with N-acetyl-D-methionine, as well as with aromatic and hydrophobic N-acetylamino acids and interacts weakly with the basic substrates. It is practically not reacted with acidic and hydrophilic N-acetyl-amino acids. Michaelis constants (K_m) and maximum reaction velocities (V_max) were calculated, using linear regression analysis, for the following substrates: N-acetyl-D-methionine, N-acetyl-D-alanine, N-acetyl-D-phenylalanine, N-acetyl-D-tyrosine, N-acetyl-D-valine, N-acetyl-D-oxyvaline, N-acetyl- D-leucine. Substrate inhibition of D-aminoacylase was displayed with N-acetyl-D-leucine (K_s = 35.5 ± 28.3 mM) and N-acetyl-DL-tyrosine (K_s = 15.8 ± 4.5 mM). Competitive inhibition of the enzyme with product–acetic acid (K_i = 104.7 ± 21.7 mM, K_m = 2.5 ± 0.5 mM, V_max = 25.1 ± 1.5 U/mg) was observed.