Pentose fructose galactose

What feature of krebs does the ppp have?

Oxidize glucose directly to CO2.

Which cofactor does the oxidation of glucose in the ppp require?

NADP+

What is the source of NADP+?

FA synthesis

Steroid synthesis

Glutathione synthesis (as antioxidant)

Biotransformation

What is the final product of ppp?

Ribose-5-p

Relation between NADPH and the ETC-

No relation because it cannot be oxidized in the ETC-> no ATP generation.

Nice fact from Vladka about ppp-

Does reciprocal conversion of monosaccharides- important for glycoprotein synthesis.

Where does the ppp occur?

cytosol

What are the phases of the ppp?

oxidative and non-oxidative

The oxidative phase of ppp-

glucose 6-P->ribulose-5-p+ CO2

2NADP+->2NADPH

1st enzyme- Glu-6-p DH

Velocity/regulation is determined by the DH reactions and the availability of NADP+

Which of the phases of the PPP is reversible?

The non oxidative

General purpose of the non oxidative phase of ppp-

Reciprocal conversion of P-monosaccharides.

Exp- 3 ribulose-5-p-> 2 fru-6-p+ glyceraldehyde-3-p

Which directions can ribulose-5-p go?

Ribose-5-p

Xylulose-5-p

Ribose-5-p is important for-

Nucleotide synthesis

Xylulose-5-p function is-

Go back to be an intermediate of glycolysis. And enter the ppp once again after some gluconeogenesis.

Fru-5-p+ glyceraldehyde-3-p

Enzymes of the weird part of non oxidative phase of ppp-

2 transferases- transketolase, transaldolase.

Hormones that induce ppp-

Insulin

Prolactin

Glu-6-p DH deficiency is-

Most widespread enzyme defect.

Course haemolytic anemia- problems with antioxidants in erythrocytes.

What is the source of fructose?

Free in fruit/honey.

Sucrose.

How does fructose get absorbed in enterocytrs?

In facilitated diffusion, using GLUT-5

General difference between the 2 pathways of fructose-

First is in the liver.

Second is in all other tissues.

1st reaction of fructose in the liver-

Fru—> fru-1-p

Fructokinase

ATP->ADP

2nd reaction of fructose in the liver-

Fru-1-p—> glyceraldehyde+ DHAP (dihydroxyacetone-p)

Aldolase B

Fate of DHAP from fructose-

Part of glycolysis.

Fates of glyceraldehyde-

1) phosphorylation to glyceraldehyde-3-p-> glycolysis.

2) reduction to glycerol-> TAG synthesis.

Why is fructose metabolism faster than glycolysis?

Bypasses phosphofructokinase, the slowest reaction of glycolysis.

That's can lead to encreased lipogenesis in the liver.

Fructose intolerance-

Congenital defect in aldolase B-> accumulation of fru-1-p.

Alternative pathway of fructose-

In other tissues-

Fru->fru-6-p

Hexokinase

Low affinity

Galactose is a ____ epimer of glucose-

4-epimer

Lactose is cleaved in the GIT by-

Lactase

Glucose and galactose are absorbed by-

secondary active transport- SGLT-1

1st step of galactose pathway-

In the liver.

Gal—>gal-1-p

2nd and rest of the steps of galactose metabolism-

Gal-1-p+UDP glucose—> UDP-Gal+ Glu-1-p

Hexose-1-p uridyltransferase.

UDP-Gal—>UDP-Glu

4-epimerase.

Then Glu-1-p converts to Glu-6-p—>glycolysis.

Galactosemia is-

Defect in hexose-1-p uridyltransferase

Galactose is converted to galactitol-couse cataract.

For what galactose is needed?

Lactose synthesis (mammary gland).

Synthesis of glycoproteins, glycolipids, proteoglycans.

What happened when we need galactose?

UDP-glucose converted—> UDP-galactose

UDP-galactose is-

Macroergic compound means it can be used for the synthesis of glycoproteins, proteoglycans, glycolipids.