Nitrate reductase enzyme is responsible for the formation of

What does the given reaction show?
Choose the correct option.

The conversion of $NO_{3}^{-} \rightarrow NO_{2}^{-} \rightarrow NH_{3}$ is called and is catalysed by:

The following reaction represents:
$\alpha$-ketoglutaric acid $+ NH_{4}^{+} + NADPH \xrightarrow{\text{Glutamate dehydrogenase}} \text{Glutamate} + H_{2}O + NADP$

In reductive amination,which of the following occurs?

In transamination,the main donor of the amino group is .....