Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of D-ribose as a cosubstrate on the uptake and metabolism of the non-growth substrate D-xylose by Saccharomyces cerevisiae ATCC 26602 was investigated. Xylose was taken up by means of low- and high-affinity glucose transport systems. In cells exposed for 2 days to a mixture of xylose and ribose, only the high-affinity system could be detected. Glucose strongly inhibited the transport of xylose by both systems. Starvation or exposure to either xylose or ribose resulted in inactivation of xylose transport, which did not occur in the presence of a mixture of ribose and xylose. A constitutive non-glucose-repressible NADPH2-dependent xylose reductase with a specific activity of ca. 5 mU/mg of protein that converted xylose to xylitol was present in a glucose-grown culture. No activity converting xylitol to xylulose or vice versa was found in crude extracts. Both xylose and ribose were converted to their corresponding polyols, xylitol and ribitol, as indicated by 13C nuclear magnetic resonance spectroscopy. Furthermore, ethanol was detected, and this implied that pathways for the complete catabolism of xylose and ribose exist. However, the NADPH2 required for the conversion of xylose to xylitol is apparently not supplied by the pentose phosphate pathway since the ethanol produced from D-[1-13C]xylose was labelled only in the C-2 position. Acetic acid was produced from ribose and may assist in the conversion of xylose to xylitol by cycling NADPH2.
 ...
PMID:Role of D-ribose as a cometabolite in D-xylose metabolism by Saccharomyces cerevisiae. 851 43

Nitrogen starvation enhances up to 8-fold the cellular level of the NADP+-dependent isocitrate dehydrogenase activity (isocitrate:NADP+ oxidoreductase (decarboxylating), IDH, EC 1.1.1.42) in the thermophilic filamentous non-N2-fixing cyanobacterium Phormidium laminosum. The enzyme was purified 650-fold to electrophoretic homogeneity from nitrogen-starved cells with an activity yield of 25% and a specific activity of 500 U (mg protein)-1. The native enzyme showed a pI of 5.9 and it was a dimer of 107 kDa consisting of two identical subunits of 53 kDa. The activity required the presence of a divalent metal cation as an essential activator, Mn2+ or Mg2+ being the most effective. The optimum temperature for activity was 55 degrees C and the Ea for catalysis was 39.7 kJ mol-1. An optimum pH for activity of 8.5 was found and the calculated pKE1, pKE2 and pKES1 of enzyme ionisation groups were 6.0, 8.9 and 6.3, respectively. Km values of 22, 50 and 24 microM were calculated for d,l-isocitrate, NADP and Mn2+, respectively, in the Mn2+-dependent reaction and 70, 32 and 159 microM for d,l-isocitrate, NADP and Mg2+, respectively, in the Mg2+-dependent reaction. The decarboxylating activity was inhibited by ATP, ADP and by its reaction products 2-oxoglutarate and NADPH2. Polyclonal antibodies raised against the pure IDH were used to assess the presence of the enzyme in cells subjected to nitrogen starvation.
 ...
PMID:Purification, properties and enhanced expression under nitrogen starvation of the NADP+-isocitrate dehydrogenase from the cyanobacterium Phormidium laminosum. 1020 82

In mammals, there are different metabolic pathways in cells that break down fuel molecules to transfer their energy into high energy compounds such as adenosine-5'-triphosphate (ATP), guanosine-5'-triphosphate (GTP), reduced nicotinamide adenine dinucleotide (NADH2), reduced flavin adenine dinucleotide (FADH2) and reduced nicotinamide adenine dinucleotide phosphate (NADPH2). This process is called cellular respiration. In carbohydrate metabolism, the breakdown starts from digestion of food in the gastrointestinal tract and is followed by absorption of carbohydrate components by the enterocytes in the form of monosaccharides. Monosaccharides are transferred to cells for aerobic and anaerobic respiration via glycolysis, citric acid cycle and pentose phosphate pathway to be used in the starvation state. In the normal state, the skeletal muscle and liver cells store monosaccharides in the form of glycogen. In the obesity state, the extra glucose is converted to triglycerides via lipogenesis and is stored in the lipid droplets of adipocytes. In the lipotoxicity state, the lipid droplets of other tissues such as the liver, skeletal muscle and pancreatic beta cells also accumulate triacylglycerol. This event is the axis of the pathogenesis of metabolic dysregulation in insulin resistance, metabolic syndrome and type 2 diabetes. In this paper a summary of the metabolism of carbohydrates is presented in a way that researchers can follow the biochemical processes easily.
...
PMID:A quick look at biochemistry: carbohydrate metabolism. 2368 95