3. Describe the two major routes by which the amino groups are removed from amino acids:...

3. Describe the two major routes by which the amino groups are removed from amino acids: transamination, oxidative deamination. Describe the role played by pyridoxal phosphate, glutamate, α–ketoglutarate, and glutamate dehydrogenase in these processes.

Expert Solution

TRANSAMINATION

It is a chemical reaction where an amino group from an amino acid is removed and transfers to a ketoacid, resulting in the formation of a new aminoacid.
deamination of most aminoacids happens this way
it converts essential aminoacids to non-essential aminoacids
catalysed by the enzyme transaminases or aminotransferases
aminotransferases are specific for individual aminoacids. most common ones are Alanine aminotransferase and aspartate aminotransferase
lysine, proline and threonine do not always undergo transamination

the reaction is as follows,

Aminoacid + alpha-ketoglutarate <-------> alpha-keto acid + glutamate

OXIDATIVE DEAMINATION

occurs only in liver
generates alpha keto acids and other oxidised products
generate ammonia as a toxic byproduct, that enters urea cycle and get neutralised
enzyme involved is dehydrogenase ( which use NAD or NADP as coenzyme) and oxidase
it differs from transamination in that it loses the amino group instead of trasfering it to another amino acid

the reaction,

Glutamate + NAD+ + H2O <--------(glutamate dehydrogenase)---------> alpha-keto glutarate + NH+4 + NADH

Role of pyridoxal phosphate (PLP) :-

it is an active form of vitamin B6 .
it acts as a coenzyme in all transamination reactions and certain deamination reactions.
aldehyde group of PLP forms a schiff base linkage with amino groups of amino acids

Glutamate :-

as discussed already it is involved in transamination
alpha keto glutarate accepts the amino group and form glutamate
this glutamate's amino group is again transfered to oxaloacetate , yields aspartate

Glutamate + oxaloacetate <---------------(glutamate degydrogenase)--------------> alpha-keto glutarate + aspartate

Glutamate degydrogenase :-

it is the enzyme invoved in the above reaction
converts glutamate to alpha keto glutarate

Alpha keto glutarate :-

it is one of the ketone derivatives of glutaric acid
also called 2 oxo- glutarate
it is an anion

gladiator answered 4 months ago

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