Characterization of a beta 1----3-N-acetylglucosaminyltransferase associated with synthesis of type 1 and type 2 lacto-series tumor-associated antigens from the human colonic adenocarcinoma cell line SW403

Previous studies have indicated that activation of a normally unexpressed beta 1----3-N-acetylglucosaminyltransferase is responsible for the accumulation of a wide diversity of both type 1 and 2 lacto-series antigens in human colonic adenocarcinomas. A beta 1----3-N-acetylglucosaminyltransferase has been solubilized from the human colonic adenocarcinoma cell line SW403 by 0.2% Triton X-100 and some of its properties have been studied. The enzyme was active over a broad pH range from 5.8 to 7.5 and had a strict requirement for Mn2+ as a divalent metal ion. Transfer of N-acetylglucosamine (GlcNAc) to lactosylceramide was optimal when assayed in the presence of a final concentration of Triton CF-54 of 0.3%. Inclusion of CDPcholine in the reaction mixture stimulated the activity by protecting the UDP[14C]GlcNAc from hydrolysis by endogenous enzymes. The kinetic parameters of the enzyme were studied. Km values for acceptors nLc4 and nLc6 were determined to be 0.19 mM for each. However, the Vmax values calculated for these acceptors were 150 and 110 pmol/h/mg protein for nLc4 and nLc6, respectively, suggesting reduced potential for further elongation as the chain length increases. The Km for UDPGlcNAc was determined to be 0.17 mM. Studies of the acceptor specificity have indicated transfer of GlcNAc occurs mainly to type 2 chain nonfucosylated structures. However, elongation of the type 1 chain structure Lc4 was also detected.     

Lessons from the genomes of extremely acidophilic bacteria and archaea with special emphasis on bioleaching microorganisms

This mini-review describes the current status of recent genome sequencing projects of extremely acidophilic microorganisms and highlights the most current scientific advances emerging from their analysis. There are now at least 56 draft or completely sequenced genomes of acidophiles including 30 bacteria and 26 archaea. There are also complete sequences for 38 plasmids, 29 viruses, and additional DNA sequence information of acidic environments is available from eight metagenomic projects. A special focus is provided on the genomics of acidophiles from industrial bioleaching operations. It is shown how this initial information provides a rich intellectual resource for microbiologists that has potential to open innovative and efficient research avenues. Examples presented illustrate the use of genomic information to construct preliminary models of metabolism of individual microorganisms. Most importantly, access to multiple genomes allows the prediction of metabolic and genetic interactions between members of the bioleaching microbial community (ecophysiology) and the investigation of major evolutionary trends that shape genome architecture and evolution. Despite these promising beginnings, a major conclusion is that the genome projects help focus attention on the tremendous effort still required to understand the biological principles that support life in extremely acidic environments, including those that might allow engineers to take appropriate action designed to improve the efficiency and rate of bioleaching and to protect the environment.