Presentation is loading. Please wait.

Presentation is loading. Please wait.

UREA CYCLE KCMUCO .2022

Similar presentations


Presentation on theme: "UREA CYCLE KCMUCO .2022"— Presentation transcript:

1 UREA CYCLE

2 OUTLINE INTRODUCTION UREA CYCLE REACTION(I-V) SUMMARY REGULATION
LINK WITH TCA CYCLE REFERENCES

3 Introduction:UREA CYCLE
Introduction:UREA CYCLE  2 NH3 + CO2 + 3 ATP + 3H2O→ urea + 2 ADP + 4 Pi + AMP Overall equation: First metabolic cycle elucidated.(1932). Also known as (Krebs-Henseleit cycle)/( ornithine cycle). It is a cycle of biochemical reactions that occurs in ureotelic organisms where the highly toxic ammonia NH3 to urea (NH2)2CO for excretion. It’s a 5 step process each with it’s driving enzyme(bolded). It occurs primarily in liver and in a small extent the kidneys. It spans two liver cellular compartment the mitochondria & cytosol compartments.

4 I. Synthesis of Carbamoyl phosphate
Description NH3(deamination)&CO2 (respiration) condense to Carbamoyl phosphate under Carbamoyl phosphate 1(CPS1) in mitochondria with NAG (N-acetylglutamate)activator. It is the rate limiting step. NB. NAG functions to increase the affinity that CPS1 has for ATP. Reaction steps

5 II. Formation of Citrulline
Description Condensation of Carbamoyl phosphate and Ornithine to Citrulline by Ornithine transcarbamoylase. Citrulline is then taken to the cytosol via a transport system. NB. Both ornithine and citrulline enter and exit the mitochondria respectively through their respective transporter systems on the mitochondrial membrane.

6 III. Synthesis of Arginosuccinate
Description Condensation of Aspartate and Citrulline by Arginosuccinate synthase. It utilizes one ATP which hydrolyzes to AMP and Pyrophosphate(Ppi) Reaction steps NB. Reaction occurs between the amino group of the aspartate and the carbonyl group of the citrulline

7 IV. Cleavage of Arginosuccinate
Description. Arginosuccinate is cleaved by Arginosuccinase to give Fumarate and Arginine. The Fumarate then links with the TCA cycle while Arginine proceeds as the immediate precursor of urea.

8 V. Urea formation Description
Arginine is cleaved by Arginase to form Urea and Ornithine. The later is taken up in the mitochondria to resume the cycle. To mitochondrion

9 SUMMARY NB. Zinc, Biotin and Manganese are all cofactors to their respective enzymes which they are associated with in the urea cycle.

10 Urea cycle regulation Urea cycle has a two level regulation
Level of enzyme synthesis. Where substrate concentration determines the rate of enzyme synthesis. Allosteric regulation Which is determined by the rate of synthesis of N-acetylglutamate an allosteric activator to Carbamoyl phosphate synthetase I,

11 Linking with the TCA cycle

12 REFERENCES Principles of biochemistry --- Lehninger 6th edition (Pg ).pdf Biochemistry ( PDFDrive ) 4thedition (Pg ).pdf Harper’s Illustrated Biochemistry ( PDFDrive ) 31stedition (Pg 679).pdf


Download ppt "UREA CYCLE KCMUCO .2022"

Similar presentations


Ads by Google