TRANSAMINATION
Originating Amino Acid
- It represents aspartate or alanine, as common examples, and is the originating amino acid (the source of the amino group).
Acceptor keto acid
- Typically, alpha-ketoglutarate. We see that it has a:
- When the originating amino acid loses its amino group, it becomes a new keto acid:
- The other product is the new amino acid (which we designate as (2)) and is L-Glutamate, the product of the addition of the amino group to alpha-ketoglutarate.
Transamination Cofactor: pyridoxal phosphate
- Pyridoxal phosphate (aka PLP, vitamin B6) is a necessary cofactor for transamination reactions.
OXIDATIVE DEAMINATION
Enzyme
- The enzyme glutamate dehydrogenase (GDH) is responsible for the oxidative deamination reaction.
Water Entrance/Ammonia Release
- Water provides the oxygen and the hydrogen necessary to oxidize alpha-ketoglutarate and protonate ammonia to ammonium (the non-toxic form of the molecule).
- We show ammonia in its charged state (as ammonium) because this is how it typically exists at physiologic pH (rather than as uncharged ammonia).
Accelerating/Decelerating Factors
- Energy deficiency states (high levels of ADP and GDP) will excite the reaction.
- Energy surplus states (high levels of ATP or GTP) will inhibit the reaction.
Transamination & Oxidative Deamination
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TRANSAMINATION AND OXIDATIVE DEAMINATION
- Transamination & Oxidative deamination are key reactions in amino acid metabolism.
Transamination
- We define transamination as the transfer of an alpha-amino group from an alpha-amino acid to an alpha-keto acid via an aminotransferase.
The two most important aminotransferases are:
- Aspartate aminotransferase (AST)
- Alanine aminotransferase (ALT)
Oxidative deamination
- Oxidative deamination is the release of ammonium via a conversion of glutamate to alpha-ketoglutarate.