Corynebacterium glutamicum SYPS-062 was an L-serine producing strain stored at our lab and could produce L-serine directly from sugar. We studied the effects of cofactors in one carbon unit metabolism-folate and VB12 on the cell growth, sucrose consumption and L-serine production by SYPS-062. In the same time, the metabolic flux distribution was determined in different conditions. The supplementation of folate or VB12 enhanced the cell growth, energy synthesis, and finally increased the flux of pentose phosphate pathway (HMP), whereas the carbon flux to L-serine was decreased. The addition of VB12 not only increased the ratio of L-serine synthesis pathway on G3P joint, but also caused the insufficiency of tricarboxylic acid cycle (TCA) flux, which needed more anaplerotic reaction flux to replenish TCA cycle, that was an important limiting factor for the further increasing of the L-serine productivity.
Citric Acid Cycle ; physiology ; Corynebacterium glutamicum ; metabolism ; Fermentation ; Folic Acid ; pharmacology ; Serine ; biosynthesis ; Vitamin B 12 ; pharmacology

No abstract available.
Citric Acid Cycle/physiology ; Cytochrome P-450 Enzyme System/metabolism ; Fatty Liver/diagnosis/pathology/ultrasonography ; Humans ; Obesity/*complications ; Severity of Illness Index

OBJECTIVETo introduce a safe and specific approach of (13)C magnetic resonance spectrum ((13)C MRS) spectroscopy and investigate the alterations in hepatic anabolism.

METHODSRelative anaplerotic, pyruvate recycling and gluconeogenic fluxes were measured by (13)C MRS isotopomer analysis of blood glucose from rats with 40% body surface area burn injury, and from rats exposed to sham injury. A short chain fatty acid, [U (13)C] propionate which was avidly extracted by the liver, was infused intravenously to deliver (13)C into the citric acid cycle. Proton-decoupled (13)C MRS of deproteinized plasma or extracts of the freeze-clamped liver were used to determine the distribution of (13)C in blood or hepatic glucose.

RESULTSThere was no difference in the multiplets detected in the glucose carbon-2 anomer from blood or liver after 45 or 60 minutes of the infusion of the propionate, indicating that steady-state isotopic conditions were achieved. Gluconeogenesis relative to citric acid cycle flux was not altered by burn injury; in both sham and burn groups the rate of glucose production was about equal to flux through citrate synthase. In the sham group of animals, the rate of entry of carbon skeletons into the citric acid cycle was about 4 times than that in the burn group. Similarly, flux through pyruvate kinase (again relative to citrate synthase) was significantly increased after the burn injury.

CONCLUSIONSSince results from analysis of the blood glucose are the same as that of the hepatic glucose, (13)C distribution in the glucose and hepatic metabolism can be assessed based on the (13)C MRS analysis of the blood glucose.

Animals ; Blood Glucose ; analysis ; Burns ; complications ; Carbon Isotopes ; Citric Acid Cycle ; physiology ; Disease Models, Animal ; Gluconeogenesis ; physiology ; Liver Diseases ; etiology ; pathology ; Liver Function Tests ; Magnetic Resonance Spectroscopy ; methods ; Male ; Probability ; Radiographic Image Enhancement ; Rats ; Rats, Sprague-Dawley ; Reference Values ; Sensitivity and Specificity