Kinetic properties of Serratia marcescens adenosine 5'-diphosphate glucose pyrophosphorylase

Protein identification in two phases of 1,3-propanediol production by proteomic analysis

Proteomic analysis by two-dimensional electrophoresis (2D)-mass spectrometry was used to identify differentially expressed proteins in the Clostridium sp. native strain (IBUN 158B) in two phases of the 1,3-propanediol (1,3-PD) production (lag phase and exponential growth phase). Intracellular protein fraction extraction conditions were standardised, as well as the 2D electrophoresis. Differences were found between both of the growth phases evaluated here. Thirty-two of the differentially expressed proteins were chosen to be identified by tandem mass spectrometry (MALDI TOF/TOF). The presence of four enzymes implicated in the 1,3-PD metabolic pathway was recorded: one from the reductive route (1,3-propanediol dehydrogenase) and three from the oxidative route (3-hydroxybutyryl-CoA dehydrogenase, NADPH-dependent butanol dehydrogenase and phosphate butyryl transferase). The following enzymes which have not been previously reported for Clostridium sp., were also identified: phosphoglycerate kinase, glucose 6-phosphate isomerase, deoxyribose phosphate aldolase, transketolase, cysteine synthetase, O-acetylhomoserine sulphhydrylase, glycyl-tRNA ligase, aspartate-β-semialdehyde dehydrogenase, inosine-5-monophosphate dehydrogenase, aconitate hydratase and the PrsA protein. The foregoing provides a novel contribution towards knowledge of the native strain for the purpose of designing genetic manipulation strategies to obtain strains with high production of 1,3-PD.

BIOLOGICAL SIGNIFICANCE

The article "Protein identification in two phases of 1,3-propanediol production by proteomic analysis" provides a novel contribution towards knowledge regarding the Colombian Clostridium sp. native strain (IBUN 158B) because this is a new approximation in comparative proteomics in two phases of the bacterial growth and 1,3-propanediol (1,3-PD) production conditions. The proteomic studies are very important to identify the enzymes that are expressed at different stages of production and therefore genes of interest in the genetic manipulation strategies; the results can be taken into account in future studies in metabolic engineering when optimising 1,3-PD production, in a cost-effective process having direct industrial applications.

A glgC gene essential only for the first of two spatially distinct phases of glycogen synthesis in Streptomyces coelicolor A3(2)

By using a PCR approach based on conserved regions of ADP-glucose pyrophosphorylases, a glgC gene was cloned from Streptomyces coelicolor A3(2). The deduced glgC gene product showed end-to-end relatedness to other bacterial ADP-glucose pyrophosphorylases. The glgC gene is about 1,000 kb from the leftmost chromosome end and is not closely linked to either of the two glgB genes of S. coelicolor, which encode glycogen branching enzymes active in different locations in differentiated colonies. Disruption of glgC eliminated only the first of two temporal peaks of ADP-glucose pyrophosphorylase activity and glycogen accumulation and prevented cytologically observable glycogen accumulation in the substrate mycelium of colonies (phase I), while glycogen deposition in young spore chains (phase II) remained readily detectable. The cloned glgC gene therefore encodes an ADP-glucose pyrophosphorylase essential only for phase I (and it is therefore named glgCI). A second, phase II-specific, glgC gene should also exist in S. coelicolor, though it was not detected by hybridization analysis.

Biosynthesis of bacterial glycogen: characterization of adenosine diphosphate glucose synthetases from Enterobacter hafniae and Aeromonas hydrophila

Enterobacter hafniae and Aeromonas hydrophila ADPglucose synthetases were purified approximately 39- and 61-fold, respectively, over the crude extract. Both enzymes were heat stable at 60 degrees C in the presence of inorganic phosphate. The molecular weights of both enzymes were approximately 200,000 which are similar to other enteric ADPglucose synthetases studied. Based on kinetic results obtained from the partially purified enzymes, the E. hafniae enzyme is activated twofold by phospho-enolpyruvate while the A. hydrophila enzyme is activated twofold by fructose 6-P and 1.5-fold by fructose 1,6 bis-phosphate. The E. hafniae enzyme activity is strongly inhibited by AMP and ADP and the inhibition can be partially reversed by P-enolpyruvate. ADP is the most effective inhibitor of the A. hydrophila enzyme and its inhibition can be partially overcome by the presence of the activators fructose 6-P and fructose 1,6-P2. These kinetic results show that the allosteric properties of the E. hafniae enzyme are distinctly different from the ADPglucose synthetases of those previously studied from bacteria of the genus Enterobacter. Although the A. hydrophila enzyme is activated by fructose 1,6-P2, its allosteric properties are quite different than those observed for ADPglucose synthetase of the Enterobacteriaceae.