Protein metabolism

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Protein metabolism – deamination, transamination, decarboxylation, transmethylation


Presentation Transcript

Protein metabolism:

Protein metabolism

Oxidative deamination:

Oxidative deamination Deamination means removal of the amino groups from amino acids. This is the mechanism where in the amino acids lose two hydrogen atoms (dehydrogenation) to form keto acids and ammonia.

Transamination :

Transamination The process of transfer of an amino group from an amino acid to an a-keto acid, resulting in the formation of a new amino acid and keto acid is known as transamination. In other words, it is deamination of an amino acid, coupled with amination of a keto acid.


Decarboxylation This refers to the removal of CO2 from the carboxyl group of amino acids. The removal of CO2 needs the catalytic action of enzymes decarboxylases and the pyridoxal phosphate coenzyme.

Transmethylation :

Transmethylation The transfer of methyl group from one compound to another is called transmethylation and the enzymes involved in the transfer are known as transmethylases.

PowerPoint Presentation:

HMP / PPP occurs when (i) NADPH2 requirement of cell increases during biosynthetic processes. (ii) When EMP pathway blocked by iodoacetate, fluorides. arsenates. (iii) When mitochondria is busy in other pathways. Most of the intermediates are similar to Calvin cycle but PPP is catabolic and oxidative process. One ATP is utilised in phosphorylation of glucose, so net gain equals to 35 ATP. (12 NADPH2)

PowerPoint Presentation:

Penrose Phosphate Pathway//HMP (Hexose mono-phosphate) Shunt/Warburg Dickens pathways: PPP is also called as Warburg - Dickens pathway / HMP shunt Phosphogluconolactone pathway /Carbohydrate degradation without mitochondria/Cytosolic oxidative decarboxylation/Horecker Racker Pathway Glycolysis & TCA cycle is the main route of carbohydrate oxidation, but Warburg & Dickens (1935) discovered an alternative route of carbohydrate break down, existing in plants, some animal tissues (Mammary glands, adipose, liver) & microbes 

PowerPoint Presentation:

Significance of HMP shunt: 1.  An intermediate erytbrose-P (4C) of this pathway is precursor of shikimic acid, which goes to synthesis of aromatic compounds and amino acids. 2. This cycle provides pentose sugars Ribose-P for synthesis of nucleotides, nucleosides, ATP and GTP.

PowerPoint Presentation:

3. A five carbon intermediate Ribulose-5-phosphate may used as CO2 acceptor in green cells. 4. This pathway produces reducing power NADPH2 for the various biosynthetic pathways, other than photosynthesis like fats synthesis, starch synthesis, hormone synthesis and chlorophyll synthesis. 5. Intermediates like PGAL and fructose-6-phosphate of this pathway may link with glycolytic reactions

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