What is the difference between an "isomerase" and a "mutase"?

Question

In biochemistry, some enzymes are called "isomerases" and some are called "mutases", and both carryout isomerization reactions, so why is there a difference in the names?

Answer 1

I would say that mutases are a type of isomerases.

Mutase is "an enzyme that catalyzes the shifting of a functional group from one position to another within the same molecule. An example of this is bisphosphoglycerate mutase" according to wikipedia http://en.wikipedia.org/wiki/Mutase

There are lots of types of isomerism. E.g. there are racemases which convert an optical isomer to the respective racemic mixture. (See http://en.wikipedia.org/wiki/Isomerase for different types of isomerases categotised according to the type of isomery).
So if the isomerization is done by shifting of a functional group from one position to another within the same molecule (regardless of the type of isomerism; optical, geometrical etc) the enzyme (which is an isomerase) is called more specifically a mutase. If it occurs through a different mechanism it is just an isomerase.

Answer 2

Isomerases are not only enzimes, they are also isoproteins.
A mutase is a simple form of protein, sinthetised it can become an enzime, along with sodium.
The difference between isomerase and mutase is that mutase procludes a methane particle and isomerase enact sodium particles (2 to 4), plus some mutases combined with calcium are forms of isomerases.