Chapter 25, Problem 25.34AP

Interpretation Introduction

Interpretation:

The step in which aspartate enter the urea cycle has to be identified, compound which eventually leave the cycle has to be determined and metabolic cycle does this compound enter has to be determined.

Concept introduction:

The cyclic biological pathway that produces urea for excretion is called urea cycle.

• Step 1: It include carbamoyl phosphate transfers its $H_{2}NC=O$ group to ornithine to give citrulline in a reaction catalyzed by ornithine transcarbamolyase.
• Step 2: Citrulline combines with aspartate to give argininosuccinate synthase
• Step 3: Argininosuccinate is split into arginine and fumarate. The enzyme is argininosuccinase.
• Step 4: The carbon-nitrogen bond of the arginine is hydrolyzed in a reaction catalyzed by arginase to give the cycle product, urea, plus ornithine, ready to repeat step 1