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Biochemistry > Uronic Acid Pathway > Flashcards

Uronic Acid Pathway Flashcards

1
Q

A pathway for conversion of glucose to glucoronic acid, ascorbic acid and pentoses

Alternative oxidative pathway for glucose but it does not lead to generation of ATP

A

Uronic Acid Pathway

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2
Q

Serves as precursor of ascorbic acid in other animals

A

Glucoronic acid

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3
Q

Humans lack this enzyme important for conversion of L-gulonolactone to L-ascorbic acid

A

L-gulonolactone oxidase

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4
Q

First step:

A

Glucose -> Glucose 6 Phosphate by enzyme Glucokinase

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5
Q

Step 2

Glucose 6-phosphate ->

by enzyme

A

Glucose-1-Phosphate

Phosphoglucomutase

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6
Q

Step 3

Glucose-1-phosphate ->

by enzyme

Used up

A

UDP glucose by enzyme UDP glucose prophosphorylase

UTP to become PPi

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7
Q

Step 4

UDP Glucose ->

by enzyme

Gives off

A

UDP glucoronate/
UDP glucoronic acid by enzyme UDP glucose dehydrogenase

2 NADH and H20

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8
Q

Step 5

UDP glucoronic acid ->

releases

A

D glucoronic acid by enzyme UDP glucoronidase

1 UDP

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9
Q

Step 6

D Glucoronic acid ->

Uses up

A

L gulonate by enzyme glucoronate reductase

NADPH -> NADP

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10
Q

In lower animals, L gulonate will be converted into

A

L gulonolactone by enzyme Aldonolactonase

L gulonolactone will be converted into 2 ketogulonolactone by enzyme Gulonolactone oxidase that is missing in humans

2 ketogulonolactone is converted into L ascorbic acid

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11
Q

In humans, L gulonic acid is converted into

A

3 keto L gulonate by enzyme L gulonate oxidase with conversion of NADP - NADPH

L xylulose will be converted into xylitol by xylulose reductase using ip NADH

D xylulose will be converted to D Xylulose 5 Phosphate by enzyme xylulose kinase

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12
Q

The metabolite from D glucoronic acid that enters PPP

A

D xylulose 5 phosphate

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13
Q

Inborn error of metabolism

One of the members of Garrod’s tetrad

A

Essential pentosuria

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14
Q

Absence of these enzymes lead to pentosuria

A

Xylitol dehydrogenase

Xylulose reductase

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15
Q

L xylulose in urine on pentosuria gives positive

A

Benedict’s test

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16
Q

Drugs that induce the pathway and increase xylulosuria

A

Barbiturates

Aminopyrine

17
Q

Deficiency of these enzymes lead to galactosemia

A

Galactose-1-phosphate uridyltransferase
Galactokinase

Build up of galactose

18
Q

Converted to glucose in the liver

May be used as test of hepatic function

A

Galactose tolerance test

19
Q

Galactose is required in the body for

A

Formation of lactose in lactation

Constituent of glycolipids, proteoglycans and glycoproteins

20
Q

Garrod’s tetrad

A

Albinism
Alkaptonuria
Cystinuria
Pentosuria

inborn errors of metabolism

Biochemistry (32 decks)

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