Glycine

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It is the simplest amino acid. It is non-essential and is glucogenic.

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Glycine

  1. 1. GLYCINE M.Prasad Naidu MSc Medical Biochemistry, Ph.D.Research Scholar
  2. 2. GLYCINE : • It is simplest aminoacid • Nonessential and glucogenic. Formation of glycine: 1. From serine 2. From threonine 3. By glycine synthase reaction
  3. 3. By Glycine synthase: NADH + + H+ NAD+ CO2 + NH4+ glycine N5 , N10 –methylene THF THF Glycine synthase is a multienzyme complex and requires PLP , NAD and THF.
  4. 4. Metabolic functions of glycine: Glycine is used for biosynthesis of 1. Heme 2. Purine ring 3. Creatine 4. Glutathione 5. As a conjugating agent 6. Glycine as neurotransmitter 7.Glycine as a constituent of protein
  5. 5. 1.Heme synthesis ALA synthase glycine + succinyl CoA δ-aminolevulinate PLP This is the rate limiting step in heme synthesis.
  6. 6. 2. Purine ring – the whole molecule of glycine is incorporated into purine ring (C4 ,C5 and N7). synthetase 5-phosphoribosyl-1-amine glycinamide ribonucleotide +GLYCINE ATP ADP + Pi
  7. 7. 3. Synthesis of creatine Arginine + Glycine Kidney Arginine- glycine transamidinase Guanidoacetate Guanidoacetate methyltransferase Liver Creatine Creatine kinase Creatine Phosphate SAM SAH ATP ADP CREATININE H2O Pi MUSCLE
  8. 8. Creatine is reversibly phosphorylated to creatine phosphate by creatine kinase and stored in muscle as high enegy phosphate. Creatinine : it is anhydride of creatine it is formed by cyclisation of creatine.
  9. 9. Serum creatinine – 0.7 -1.4 mg/dl Urine creatinine – 1- 2 g/day Serum creatinine concentration is not influenced by endogenous or exogenous factors, so used as a more reliable indicator of renal function.
  10. 10. 4.Synthesis of glutathione
  11. 11. Superoxide dismutase Peroxidase O2 - (superoxide) H2O2 H2O i)Freeradical scavenging 2GSH GS– SG Glutathione reductase 2NADP+ NADPH+H+ Glucose -6-phosphate GPD By scavenging free radicals it maintains RBC membrane integrity.
  12. 12. iii)Involved in amino acid transport – Meister cycle iv)Insulin inactivation by hepatic insulin glutathione transhydrogenase Insulin(A+B chains)+ 2GSH GS—SG+A chain +B chain v) Activation of enzymes : Many enzymes having –SH in active site are kept in the active form by glutathione. Ex: glyceraldehyde -3-P dehydrogenase
  13. 13. vi)Met-hemoglobin: glutathione is necessary for the reduction of met-Hb(ferric) normal Hb (ferrous state). The met-Hb is can not transport oxygen . 2Met-Hb-(Fe3+ ) +2 GSH 2 Hb-(Fe2+) + 2H+ + GSSG
  14. 14. 5. Conjugating agent It is used for conjugating bile acids so that their amphipathic property is increased. Cholic acid + Glycine glycocholic acid Chenodeoxycholic acid glycochenodeoxycholic + Glycine acid Glycine + Benzoic acid benzoyl glycine ( hippuric acid)
  15. 15. 6.Glycine as neurotransmitter:  It is a neurotransmitter in the brainstem and spinal cord.  At moderate levels it disrupts neuronal traffic; but at very high levels it causes overexcitation
  16. 16. 7.Glycine as a constituent of protein  It is seen where the polypeptide chain bends or turns.  In collagen , every third aminoacid is glycine.

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