Which enzyme is associated with oxidation and reduction reactions in a cell?

In most plant cells,most enzymes have their optimum activity at: (in $^\circ C$)

The curve given below shows enzymatic activity in relation to three conditions ($pH$,temperature and substrate concentration). What do the two axes ($x$ and $y$) represent?

At which temperature do enzymes lose their native conformation?

Basically how many types of enzymes have been recognised by the International Union of Biochemistry?

Match the following Column-$I$ with Column-$II$ and select the correct option.

Column-$I$	Column-$II$
$(A)$ Transferases	$(i)$ $H_4P_2O_7$ related reactions
$(B)$ Lyases	$(ii)$ Hexokinase
$(C)$ Isomerases	$(iii)$ Cytochrome oxidase
$(D)$ Ligases	$(iv)$ Aldolase
$(E)$ Oxidoreductases	$(v)$ Glucose-$6$-phosphate $\rightarrow$ Fructose-$6$-phosphate