Q.What do the four digits in an enzyme code (EC number) represent?

[!TLDR]

The question asks what the four digits of an enzyme's EC number stand for. …

Every enzyme recognised by the International Union of Biochemistry is given a unique Enzyme Commission (EC) number consisting of four digits separated by full stops, and each digit narrows the enzyme's identity down a further level. The first digit specifies which of the six major enzyme classes (oxidoreductases, transferases, hydrolases, lyases, isomerases, or ligases) the enzyme belongs to, based on the general type of reaction it catalyses. The second digit specifies the sub-class, giving more detail about the exact kind of group or bond involved in that reaction. The third digit specifies the sub-subclass, narrowing the reaction type down still further. Finally, the fourth digit is simply the serial number assigned to that particular enzyme within its …

• Reversing the order and thinking the last digit is the broadest category rather than the most specific one. …