GLYCINE

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• GLYCINE

M.Prasad Naidu MSc Medical Biochemistry, Ph.D.Rese
arch Scholar
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• GLYCINE
• It is simplest aminoacid
• Nonessential and glucogenic.
• Formation of glycine
• From serine
• From threonine
• By glycine synthase reaction

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• 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.

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• Metabolic functions of glycine
• Glycine is used for biosynthesis of
• Heme
• Purine ring
• Creatine
• 4. Glutathione
• 5. As a conjugating agent
• 6. Glycine as neurotransmitter
• 7.Glycine as a constituent of protein

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• 1.Heme synthesis
• ALA synthase
• glycine succinyl CoA
  d-aminolevulinate
• PLP
• This is the rate limiting step in heme synthesis.

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2. Purine ring the whole molecule of glycine is
incorporated into purine ring (C4 ,C5 and N7).

synthetase 5-phosphoribosyl-1-a
mine glycinamide
ribonucleotide GLYCINE
ATP ADP Pi
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• 3. Synthesis of creatine
• Arginine Glycine
• Kidney
  Arginine- glycine transamidinase
• Guanidoacetate
• Guanidoacetate methyltransferase
  Liver
• Creatine
• 
  Creatine kinase
• Creatine Phosphate

SAM
SAH
H2O
ATP
CREATININE
ADP
MUSCLE
Pi
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• 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.

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• 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.

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4.Synthesis of glutathione
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• Superoxide dismutase Peroxidase
• O2- (superoxide) H2O2 H2O
• i)Freeradical scavenging 2GSH GS
  SG
• Glutathione reductase
• 2NADP NADPHH
• Glucose -6-phosphate GPD
• By scavenging free radicals it maintains RBC
  membrane integrity.

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• iii)Involved in amino acid transport Meister
  cycle
• iv)Insulin inactivation by
• hepatic insulin glutathione transhydrogenase
• Insulin(AB chains) 2GSH GSSGA
  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

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• 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

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• 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)

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• 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

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7.Glycine as a constituent of protein

• It is seen where the polypeptide chain bends or
  turns.
• In collagen , every third aminoacid is glycine.