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Lesson 18
Nitrogen Metabolism 5
| Term | Definition |
|---|---|
| N-acetyl-glutamate | activates carbamoyl-phosphate 1 (necessary activator of urea cycle) |
| What activates N-acetyl-glutamate synthesis? | Arginine |
| What is the substrate of N-acetyl-glutamate synthesis? | glutamate |
| What causes NAG synthetase deficiency? | Primary mutation in NAGS gene, or secondary - mutations in mitochondria which affect NAGS function |
| How to restore function when there is a NAGS deficiency? | Carbamoylglutamate |
| What is the most common urea cycle mutation? | Issues with ornithine transcarbamoylase - very deadly |
| Characteristics of arginase issues | -episodic hyperammonemia -often healthy in childhood because arginine is used more in childhood |
| Where is ammonia filtered? | Liver acinus - where portal vein and hepatic artery enter |
| Why does the liver endothelial lining have holes? | allows direct contact between blood and hepatocytes |
| First segment of liver acinus | -contains urea cycle enzymes and glutaminase -low affinity, high capacity |
| Second segment of liver acinus (perivenous scavenger cells) | -contains glutamine synthetase -high affinity, low capacity -grabs remaining ammonia, supplies glutamine |
| How is arginine made? | Protein turnover and urea cycle (argininosuccinate) |
| What does arginine make? | Nitric oxide, controls blood pressure |
| Creatine | made from arginine; phosphorylated and stored in muscles, becomes and ATP source |
| Creatinine | byproduct of creatine -> ATP, produced fairly constant, sign of kidney function |
| How is glutamate made? | -transamination of a-ketoglutarate -reductive amination of a-ketoglutarate -hydrolysis of glutamine |
| How is glutamine made? | glutamine synthetase from glutamate |
| How is aspartate made? | -transamination of oxaloacetate -hydrolysis of asparagine |
| How is asparagine made? | Asparagine synthetase - glutamine plus aspartate, uses NH3 tunnel |
| How is alanine made? | Transamination of pyruvate |
| How is proline made? | Multi-step process, one intermediate is a glutamate semi-aldehyde which can also be used to make ornithine |
| How is hydroxyproline made? | Proline hydroxylase uses O2 to add OH group to proline residue |
| How is hydroxyproline related to scurvy? | Hydroxyproline necessary for collagen; proline hydroxylase needs to be regenerated by Vitamin C; low Vitamin C = low hydroxyproline = unstable collagen = scurvy |
| How is serine made? | conversion from a sugar metabolism intermediate (3-phosphoglycerate) |
Created by:
CGraybosch
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