350

chapter 17

Protein and Amino Acid Metabolism

Glycolysis

COO-

1

Phosphoglycerate

COO

I

HC— OH

-

1

dehvdroaenase

h

H

2

C— o — ®

NAD+

NADH + H+

H

2

C— o-

3-Phosphoglycerate

COCT

+

I

H

3

N<j5H

CH— OH

3-Phosphohydroxypyruvate

^ G lu tam ate

Phosphoserine

transam inase

^ -a-K etoglu tarate

Phosphoserine

phosphatase

R

HO

COO-

I

h

2

n (J;h

HjC—o—®

L-Seri ne

3-Phosphoserine

FIGURE 17-11

Synthesis of serine from 3-phosphoglycerate. P = POj- ;

Pj =

HPO^A

Decarboxylation of ornithine to putrescine by ornithine

decarboxylase serves as a source of the polyamines

spermidine and spermine.

Ornithinemia

results from

deficiency of ornithine aminotransferase or ornithine

decarboxylase. Ornithine aminotransferase deficiency is

associated with gyrate atrophy of the choroid and retina

(Chapter 38). Proline and hydroxyproline (produced by

posttranslational modification) are major constituents

COO-

F IG U R E 1 7 -1 2

Metabolism of proline (1) A'-pyrroline-5-carboxylate (P5C) synthase; (2) ornithine aminotransferase; (3) P5C

reductase; (4) proline oxidase; (5) P5C dehydrogenase; (

6

) ornithine decarboxylase.