Characterization of the recombinant diaminobutyric acid acetyltransferase from Methylophaga thalassica and Methylophaga alcalica

Abstract

Diaminobutyric acid acetyltransferase (EctA) catalyzes the acetylation of diaminobutyric acid to γ-N-acetyl-α,γ-diaminobutyrate with acetyl coenzyme A. This is the second reaction in the ectoine biosynthetic pathway. The recombinant EctA proteins were purified from two moderately halophilic methylotrophic bacteria: Methylophaga thalassica ATCC 33146 T and Methylophaga alcalica ATCC 35842T. EctA found in both methylotrophs is a homodimer with a subunit molecular mass of c. 20 kDa and had similar properties with respect to the optimum temperature for activity (30°C), Km for diaminobutyrate (370 or 375 μM) and the absence of requirements for divalent metal ions. The enzyme from M. thalassica exhibited a lower pH optimum and was inhibited both by sodium carbonates and by high ionic strength but to a lesser extent by copper ions. © 2008 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.