What amino acid other than alanine can be converted by trans

What amino acid, other than alanine, can be converted by transamination of a gluconeogenic precursor? Calculate the cost (in ATP equivalents), of converting two molecules of this amino acid to glucose Some organisms can anaerobically convert glycerol to pyruvate. Could homolactic or alcoholic fermentation regenerate sufficient NAD^+ to support this pathway?

Solution

1. For gluconeogenesis, pyruvate, oxaloacetate glycerol and 3 phosphoglycerate can be precursors. Out of which, alanine is formed from pyruvate by transamination. Aspartate is synthesised from oxaloacetate by transamination.

2. The cycle by which aspartate helps in producing glucose is called the malate aspartate shuttle. The malate-aspartate shuttle generates NADH in the mitochondrial matrix, producing more number of ATPs produced in glycolysis (3/NADH), thus, resulting in a net gain of 38 ATP / glucose metabolized.

3. Glycerol + 2 NAD+ + Pi + ADP pyruvate + ATP + H2O + 2 NADH + H+

Enzymes involved are - Glycerol kinase and glycerol phosphate dehydrogenase.

Here, only 2 molecules of NADH are required in converting glycerol to pyruvate. Both homolactic and alcoholic fermentation can regenerate 2 molecules of NADH