Metabolism of Monosaccharides and Disaccharides · 2019-10-29 · 10/29/2019 1 Metabolism of...

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10/29/2019 1 Metabolism of Monosaccharides and Disaccharides Fructose Metabolism 10% of the daily calorie intake Sources: sucrose, Fruits, honey, highfructose corn syrup Entry into cells is NOT insulin dependant. Does NOT promote the secretion of insulin 1 3 2

Transcript of Metabolism of Monosaccharides and Disaccharides · 2019-10-29 · 10/29/2019 1 Metabolism of...

Page 1: Metabolism of Monosaccharides and Disaccharides · 2019-10-29 · 10/29/2019 1 Metabolism of Monosaccharides and Disaccharides Fructose Metabolism • 10% of the daily calorie intake

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Metabolism of Monosaccharides and Disaccharides

Fructose Metabolism

• 10% of the daily calorie intake 

• Sources: sucrose, Fruits, honey, high‐fructose corn syrup

• Entry into cells is NOT insulin dependant.

• Does NOT promote the secretion of insulin

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Hexokinase has high Km toward fructose

Fructokinase Aldolase B Aldolase AAldolase B

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Human expresses three forms of aldolase

Aldolase B

• Liver, kidney, small intestine

• Substrate

Fruc. 1 phpsphate

Also

Fruc. 1,6 bisphospate

↓ac vity fructose intolerance

Aldolase A

• In most tissues

• Substrate

Fruc. 1,6 bisphospate

Not

Fruc. 1 phpsphate

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Disorders of Fructose Metabolism• Fructokinase Deficiency  essential fructosuria

– Accumulation of fructose  fructosuria

– Benign condition

• Aldolase Deficiency  hereditary fructose intolerance, (Fructose Poisoning)

– Severe disturbance  in liver and kidney metabolism

– ↑↑↑ Fruc. 1‐Phosph.  drop in Pi drop in ATP ↑↑ AMP ↑ degrada on of AMP

– Hypoglycemia and lacticacidemia

– Hepatic failure

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Conversion of glucose to fructose via sorbitol

Aldose reductase

Sorbitol Dehydrogenase

Aldose Reductase:Found in many  tissues;Lens, retina, schwan cells, liver, kidney, ovaries, and seminal vesicle

Sorbitol Dehydrogenase:Liver, ovaries and seminal vesicles

Fructose : the major energy source for sperm cells

H

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Galactose Metabolism

• Epimer of glucose

• Sources: component of lactose,

glycolipids and glycoproteins

• UDP Galactose; an Intermediate

in Galactose Metabolism

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UDP Galactose; an Intermediatein Galactose Metabolism

Galactose Metabolism

1

2

3

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Galactose + ATP                       Gal. 1‐Phosph   ADP

Gal 1‐Phosph + UDP Glc.           UDP‐ Galactose + Glc1‐Phosph

UDP Galactose                                 UDP Glucose

Galactokinase

transferase

epimerase

GGal 1‐phosph. uridyl Transferase 

GALT

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Disorders of Galactose Metabolism• Deficiency of GALT   classic Galactosemia

• Accumulation of Galactose 1‐Phosphate and galactose

• Similar consequences to those in fructose intolerance

• Galactose …… Galactitol

• Deficiency of Galactokinase

• Accumulation of Galactose …… Galactitol

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Lactose Synthesis• Lactose is   Galactosyl β (1→4) glucose

• Galactosyl β (1→4) glucose is found in glycolipids and glycoproteins

UDP Gal. + Glucose                       Lactose + UDP

• Lactose Synthase: complex of 2 proteins

Galactosyl transferase (Protein A)

α‐lactalbumin (Protein B)

In glycolipids synthesis

UDP‐Gal + N acetyl glucosamine            N‐acetyllactosamine

Lactose Synthase

Protein A

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Mannose conversion to Fructose 6‐phosphate

• Mannose 

• Mannose 6‐Phosphate

• Fructose 6‐Phosphate

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Metabolism of Alcohol

ADH: Alcohol DehydrogenaseALDH: Acetaldehyde DehydrogenaseACS: Acetyl CoA Synthetase

How do you prepare acetic acid from ethanol in organic chemistry? 

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