At which temperature do enzymes lose their native conformation?

According to the generally accepted rule,the rate of reaction doubles or halves for every $.........^{\circ}C$ change in temperature.

Select the correct match for $X$ and $Y$:

Column $X$	Column $Y$
$(1)$ Aldolase	$(P)$ Hydrolases
$(2)$ Hexokinase	$(Q)$ Ligases
$(3)$ Succinic dehydrogenase	$(R)$ Lyases
$(4)$ Fructose isomerase	$(S)$ Oxidoreductases
$(5)$ Lactase	$(T)$ Transferases
$(6)$ Acetyl $CoA$ synthetase	$(U)$ Isomerases

In the modern system of nomenclature,which one of the following enzymes occupies the $1^{st}$ position?

Fumarase enzyme belongs to which class?

The given graph shows the effect of substrate concentration on the rate of reaction of the enzyme green-gram-phosphatase. What does the graph indicate?