Regulation of capsular polysialic acid biosynthesis by temperature in Pasteurella haemolytica A2

The capsular polysaccharide of Pasteurella haemolytica A2 consists of a lin ear polymer of N-acetylneuraminic acid (Neu5Ac) with alpha(2-8) linkages. T he production of this polymer is strictly regulated by the growth temperatu re and above 40 degrees C no production is detected. Analysis of the enzyma tic activities directly involved in its biosynthesis reveals that Neu5Ac ly ase, CMP-Neu5Ac synthetase and polysialyltransferase are involved in this r egulation. Very low activities were found in P. haemolytica grown at 43 deg rees C (at least 25 times lower than those observed when the growth tempera ture was 37 degrees C). The synthesis of these enzymes increased rapidly wh en bacteria grown at 43 degrees C were transferred to 37 degrees C and decr eased dramatically when cells grown at 37 degrees C were transferred to 43 degrees C. These findings indicate that the cellular growth temperature reg ulates the synthesis of these enzymes and hence the concentration of the in termediates necessary for capsular polysaccharide genesis in P. haemolytica A2. (C) 1999 Federation of European Biochemical Societies.