Cloning, expression, and characterization of acetate kinase from Lactobacillus sanfranciscensis

In the metabolism of Lactobacillus sanfranciscensis, the acetate kinase (AK ) is a key enzyme and responsible for dephosphorylation of acetyl phosphate with the concomitant production of acetate and ATP. The L. sanfranciscensi s ack gene was identified by PCR methods. It encodes a 397 amino acid prote in sharing 56% similarity with Bacillus subtilis AK. Whereas cotranscriptio n of ack and pta (phosphotransacetylase) is reported in previously characte rised organisms, the L. sanfranciscensis ack gene is not located in direct neighbourhood to the encoding gene. AK was heterologously expressed in E. c oli and characterised by its vmax and Km values and by the dependence of en zyme activity on temperature and pH. Based on this data the in vivo role of the enzyme is discussed.