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Class 10 uronic acid pathway
The document provides an overview of the uronic acid pathway, detailing its definition, occurrences, and biochemical significance, particularly in the context of detoxification and the synthesis of mucopolysaccharides. It also discusses metabolic reactions, including the conversion of glucose to glucuronic acid, and the implications of xylitol dehydrogenase deficiency, leading to essential pentosuria. Furthermore, the regulation of the pathway by certain drugs is mentioned, noting their effects on uronic acid synthesis and xylulose excretion.
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Class 10 uronic acid pathway
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- 2. Objectives • Definition • Occurrenceand tissue distribution • Biomedical importance • Metabolic reactions • Clinical importance
- 3. Definition • Alternative pathwayfor oxidation of glucose • Result in the formation of Glucuronic acid, Keto-pentose sugar (Xylulose) and Vitamin C (But not in human ) Occurs in cytosol of Liver and adipose tissue
- 4. Biochemical function orsignificance • Major function is to produce D- Glucuronic acid , which is required for Detoxication & Synthesis of Mucopolysaccharides • There is no energy production • Due to lack of enzyme Gluconolactone oxidase, can not produce Ascorbic acid in human • Associated with IEM Essential pentosuria
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- 6. Activation of GlucoseGlucose Glucose-1-phosphate UDP- Glucose ATP ADP Glucokinase Hexokinase UTP PPi 2Pi UDPG pyro phosphorylase Spontaneous hydrolysis of phosphate bond Provides reaction energy Only energy cost in Pathway Glucose -6-phosphate Phosphoglucomutase
- 7. Oxidation of GlucoseUDP-Glucose D- Glucuronate L- Gulonate NAD NADH + H UDP Glucose DH NADPH + H NADP Ascorbic acid L- Gulonic DH 1. UDP glucose is oxidised To UDP Glucuronate – used for detoxication & MPS synthesis 2. UDP hydrolysed 3. Reduction 4. Oxidation to Vit C UDP- Glucuronate GlucuronidaseH2O UDP L- Gulonolactone oxidase
- 8. Conversion to pentoseL-Gulonate L- Xylulose L - Xylitol NAD+ NADH+H Dehydrogenase NADPH + H NADP Xylulose Xylulose DH/ reductase Enters in to HMP pathway 3- Keto L – Gulonate Decarboxylase CO2 NAD NADH+H Xylulose 5 P Kinase ADP ATP reductase Essential Pentoseuria
- 9. Essential Pentosuria • CommonIE of Uronic acid pathway • Cause: Xylitol DH or Reductase deficiency • Increased excretion of L-xylulose • Diagnosis: Benedict’s test positive but Glucose oxidase strip negative • Loading Test: Glucuronic acid increases Xylulose excretion • Harmless condition but need to be differentiated from DM.
- 10. Regulation • Administration ofdrugs like Chlorobutanol and Barbital significantly increases Uronic acid synthesis • Drugs like Amino Pyrine & Amido pyrine increases excretion of xylulose.