The document summarizes three metabolic pathways: the pentose phosphate pathway, glucuronate pathway, and lactose synthesis. The pentose phosphate pathway produces NADPH and pentoses like ribose-5-phosphate. The glucuronate pathway is an alternative glucose oxidation pathway that produces UDP-glucuronate for detoxification and ascorbic acid in some animals. Lactose synthesis occurs in the mammary gland golgi and involves the enzymatic conversion of glucose and UDP-galactose to produce the milk sugar lactose.

1. METABOLISM - I
•Pentose Phosphate Pathway
•Glucuronate Pathway
•Lactose Synthesis
Submitted by : Diwakar Sharma
M.Sc Biochemistry, Semester – II, First Year

2. Pentose Phosphate Pathway
also called the phosphogluconate pathway or
the hexose monophosphate pathway

3. Pentose Phosphate Pathway
 OVERVIEW:-
 NADPH production
Glutathione reduction (E), fatty acid/cholesterol synthesis (L)
 Glycolytic intermediates
Fructose-6-phosphate, glyceraldehyde-3-phosphate
 Ribose-5-phosphate & Xylulose , Ribulose (Pentoses)
Nucleotide synthesis (nucleated cells)

4. Pentose Phosphate Pathway
•Glycolysis to PPP

5. Pentose Phosphate Pathway
•Oxidative Phase
Source: Lehninger

6. Pentose Phosphate Pathway
•Non-oxidative Phase
Source: Lehninger

7. Pentose Phosphate Pathway
•Glucose 6-Phosphate Is Partitioned between Glycolysis and the PPP
Source: Lehninger

8. Glucuronate Pathway
Also called uronic acid pathway

9. Glucuronate Pathway
 An alternative pathway for the oxidation of glucose
that does not provide a means of producing ATP, but
is utilized for the generation of the activated form of
glucuronate, UDP-glucuronate which is mainly used
for detoxification of foreign chemicals and for the
synthesis of Mucopolysaccharides.
 This pathway also produces Ascorbic Acid in certain
animals.
 The unutilized Glucuronate produced in this pathway
is converted to Xylulose 5-phosphate which is further
metabolized through PPP.

10. 1. Formation of UDP glucose
Steps:
2. Formation of Glucuronic acid

11. Glucuronate Pathway
 In animals synthesizing this vitamin
C
 In humans

 PPP...

13. Lactose Synthesis
Also called milk sugar.

14. Lactose Synthesis
 Lactose, the disaccharide of milk, consists of
galactose joined to glucose by a β-1,4-glycosidic
linkage.
 Lactose is hydrolyzed to these monosaccharides by
lactase in human beings and by β-galactosidase in
bacteria.

15. 1
UDP Gal
translocator
GLUT-1
Galactosyl-
transferase
Lactose
SynthaseUMP
translocator

16. Lactose Synthesis
 Glucose is first converted to UDP-galactose via the enzyme
galactose-1-phosphate uridylyltransferase.
 UDP-galactose is then transported into the Golgi by the UDP
galactose translocator, an antiporter which uses facilitated transport
to move UDP galactose into the Golgi and exports UMP.
 Once inside the Golgi, the UDP galactose and glucose (which moves
into the golgi via the GLUT-1 transporter) become substrates for the
lactose synthase enzyme complex, comprised of the enzymatic
subunit, galactosyltransferase with its regulatory subunit, Alpha-
lactalbumin.
 Lactose synthase creates lactose through bonding galactose from
UDP to glucose through a glycosidic bond.
 Although GT is found in many tissues in the body, Alpha-
lactalbumin is only found on the inner surface of the Golgi in the
mammary glands, limiting lactose production to the mammaries.