Substrate inhibition sequence comparisons

STR was first purified by Treimer and Zenk [78, 79] and Mizukami et al. [80] from cell cultures of C. roseus. The enzyme was found to have a high substrate specificity, and to suffer no inhibition by end-product alkaloids, such as vindoline and catharanthine [78-80]. It was observed that STR occurred as different isoenzymes [81, 82], and the subcellular localization was determined to be the vacuole [83]. The complete mRNA sequence of Str was determined by Pasquali et al. [84], who also showed that STR is encoded by a single-copy gene, indicating that the above mentioned isoenzymes are formed post-translationally from a single precursor. Comparison of the primary structure of the STR protein with the amino acid sequence deduced from the Str mRNA showed the... 

Bryant and DeLuca (5) purified and characterized a Type I nitroreductase from Enterobacter cloacae. The protein is a monomer of approximately 27 kDa, it has a loosely bound FMN cofactor and uses NAD(P)H as an electron donor. The substrate range of the enzyme includes nitrofurans, nitrobenzenes, nitrotoluenes and quinones. The enzyme appears to produce the hydroxylamino derivative of nitroflirazone under aerobic conditions, but the product was not thoroughly characterized. Under anaerobic conditions the product is the amine. The authors did not test the effect of metals on enzyme activity, and no inhibition studies were reported. Therefore, it is not known if this enzyme is a metalloprotein. The gene encoding the Enterobacter reductase was cloned and sequenced (7). The authors found a 651 base pair open reading frame corresponding to a protein of 23.9 kDa. Comparison of the Enterobacter and Salmonella amino acid sequences revealed 88% sequence identity between the two proteins (7). 

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