Transcript Glycine - SlideBoom

GLYCINE
M.Prasad Naidu
MSc Medical Biochemistry,
Ph.D.Research Scholar
GLYCINE :
• It is simplest aminoacid
• Nonessential and glucogenic.
Formation of glycine:
1. From serine
2. From threonine
3. By glycine synthase reaction
By Glycine synthase:
NADH
CO2 + NH4+
++
H+
N5 , N10 –methylene THF
NAD+
glycine
THF
Glycine synthase is a multienzyme complex and
requires PLP , NAD and THF.
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
1.Heme synthesis
ALA synthase
glycine + succinyl CoA
δ-aminolevulinate
PLP
This is the rate limiting step in heme synthesis.
2. Purine ring – the whole molecule of glycine is
incorporated into purine ring (C4 ,C5 and N7).
synthetase
5-phosphoribosyl-1-amine
+GLYCINE
ATP
glycinamide ribonucleotide
ADP + Pi
3. Synthesis of creatine
Arginine + Glycine
Kidney
Arginine- glycine
transamidinase
Guanidoacetate
SAM
Guanidoacetate methyltransferase
HO
SAH
2
ATP
Liver
Creatine
CREATININE
ADP
MUSCLE
Creatine
kinase
Pi
Creatine Phosphate
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.
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.
4.Synthesis of glutathione
Superoxide dismutase
O2- (superoxide)
Peroxidase
H2O2
i)Freeradical scavenging
H2O
2GSH
GS– SG
Glutathione reductase
2NADP+
NADPH+H+
Glucose -6-phosphate
GPD
By scavenging free radicals it maintains RBC
membrane integrity.
iii)Involved in amino acid transport – Meister cycle
iv)Insulin inactivation by
hepatic insulin glutathione transhydrogenase
Insulin(A+B chains)+ 2GSH
chain
GS—SG+A chain +B
v) Activation of enzymes : Many enzymes having –SH in
active site are kept in the active form by glutathione.
Ex: glyceraldehyde -3-P dehydrogenase
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
5. Conjugating agent
It is used for conjugating bile acids so that their
amphipathic property is increased.
Cholic acid + Glycine
glycocholic acid
Chenodeoxycholic acid
+ Glycine
glycochenodeoxycholic
acid
Glycine + Benzoic acid
benzoyl glycine
( hippuric acid)
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
7.Glycine as a constituent of protein
 It is seen where the polypeptide chain bends or turns.
 In collagen , every third aminoacid is glycine.