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20 Cards in this Set
- Front
- Back
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synthesis of cysteine
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serine : carbon skeleton
methionine --> homoscystein: thiol group L methionine S adenyl methionine s adenyl homocysteine l homocysteine l cystathione l homoserine + l cysteine |
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functions of cysteine
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1. 1ry amino acid
2. glucogenic 3. formation of bile salts 4. thioethanolamine 5. cystine 6. thiol group forms the active group of many enzymes 7. PAPS 8. glutathione synthesis |
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cysteine glucogenic
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cysteine
cysteine sulfunic acid sulfinyl pyruvic acid pyruvic acid [iminoprorionate] |
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cysteine bilesalts
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cysteine
cysteine sulfunic acid cysteic acid taurine |
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cysteine cystine
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cystine reductase
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active group of many enzymes (cysteine)?
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glyceraldehyde 3 phosphate dehyrdogenase
fatty acid synthase multienzyme complex |
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PAPS used for synthesis of
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s containing compounds eg
GAGS and sulfolipids |
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glutathione structure
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glutamyl-cysteinyl-glycine
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functions of glutathione
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1. transport of AA thru CM
2. antioxidant, removes reactive o2 species eg H2O2 by glutathione reductase/peroxidase 3. coenzyme for eg maleylacetoacetate isomerase glutathione insulin transhydrogenase 4. keeps the thiol group of many proteins in the reduced state 5. detoxication of toxins eg bromobenzene |
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cysteinuria
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- excessive excretion cystine
- defect in renal reabsorption of : cystine, lysine, ornithine, arginine - cystine stones formed in the renal tubules |
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cystinosis
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- rare lysosomal disorder
-defective carrier mediated transport of cystine - cystine deposited as crystals in tissues and organs --> damage --- RENAL FAILURE --> death |
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functions of methionine
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condenses with ATP to form SAM
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functions of sam
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used in many transmethylation reactions
a) Phosphatidyl ethanolamine --> phosphatidyl choline b) norepinephrine --> epinephrine c) guanidoacetic acid --> creatine d) n-acetyl serotonin --> melatonin |
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metabolism of homocysteine (after transmethylation)
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1. SALVAGE PATHWAY
2. TRANSSULFURATION 3. HYDROLYSIS |
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salvage pathway of homocysteine
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remythylation of homocysteine --> methionine
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trassulfuration/ how is methionine glucogenic
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homocysteine
cystathionine homoserine alphaketobutyrate proprionyl coA |
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hydrolysis of homocysteine
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methionine and cysteine present in adequate amounts --> activate homocysteine desulfhydrase
homocysteine alphaketobutyrate proprionyl coA |
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metabolic errors of methionine and homocysteine
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homocystinuria type I
cystathioninuria |
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homocystinuria type I
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-deficiency of cystathionine synthase
- high level plasma methionine - excretion of lots of methionine, s adenosyl methionine, homocystine* - mental retardation, thrombosis, osteoporosis, dislocated lens |
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cystathioninuria
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decreased activity of cystathionase
- excretion of large amounts of cystathionine in urine |
