5 Glutamic acid, glutamine, and the relationship to proline, arginine, and histidine

5 Glutamic acid, glutamine, and the relationship to proline, arginine, and histidine
Glutamate is nonessential and glucogenic
– it gives 2-oxoglutarate readily by oxidative deamination or transamination
Glutamine is an amide of glutamate

Direct oxidative deamination of glutamate by dehydrogenation
The reaction is catalysed by the mitochondrial enzyme glutamate dehydrogenase (GLD). It requires either NAD+ or NADP+ as coenzyme, and its activity in mitochondria is high.

Glutamate is widely used as a food additive to enhance flavour of dishes, particularly in Chinese cookery in high amounts.
Excess in the diet (1 – 5 g of glutamate in one dose, e.g. in the form of "Von-Ton“ soup) can cause unpleasant feelings in sensitive persons – the Chinese restaurant syndrome.

Arginine
is nonessential and glucogenic
– nonessential in adult man (required in the diet during the growth)
– degraded to 2-oxoglutarate
In the liver, arginine is hydrolyzed to ornithine and urea. Ornithine serves as the substrate for ureosynthetic cycle