A SHORTCUT TO NAMING ENZYMES – USMLE Step 1

by / Sunday, 10 July 2011 / Published in Biochemistry, USMLE Advice

One of the keys to success in medicine is learning the patterns instead of simply memorizing… When you recognize a pattern that you can apply to 95% of everything you do, it really does make your life easier, and it ensures that when you sit to write your Step 1 exam you won’t be struggling to figure out trivial information.

Here is a great strategy you can use to help you master the art of naming enzymes, which will help you accurately name almost all enzymes you come across in medicine.

 

First name of the enzyme = the name of the substrate

Last name of the enzyme = what you did to the substrate

And here’s everything you can “do” to the substrates…

Kinase – uses ATP to phosphorylate the substrate, all kinases use magnesium as a co-factor

 

Phosphorylase – uses free PO4 – symbol is ‘Pi’

 

Isomerase – creates an isomer of the substrate (same makeup diff structure) – glucose –> fructose or fruc–>gluc

 

Epimerase – creates an ‘epimer’ – ie same makeup and structure (ex glucose and galactose , but they vary around only 1 carbon molecule).   Eniantomer = mirror image of something, we have L-amino acids and D-sugars.

 

Mutase – moves sidechain of 1carbon to another (intrachain movement).  ex – methylmalonyl CoA mutase

 

Transferase– moves a sidechain from 1 substrate to another (is interchain movement)

 

Transaminases – used in all AA metabolism (use B6 as a co-factor) – clue for b6 deficiency is neuropathy… DOC for neuropathy is amytryptaline, shooting neuropathy is carbamazepine (review)

 

Lyase – breaking a carbon-carbon bond (requires ATP)

 

Carboxylase – makes a carbon-carbon bond (uses C02 to make this bond).  These use Biotin as their co-factor

 

Synthase – no bonds broken, things just stacked together (doesnt use ATP)

 

Synthetase – same but requires ATP

 

Dehydrogenase – means there’s a co-factor in the rxn (NAD, NADH, FAD, FADH, etc).. .a hydrogen is going to be lost from the reaction

 

Hydrolase – water is used to break the bond ex. glucose-6-phosphatase

 

Thio – a sulfur bond was broken when ‘thio’ is in the name

 

All it takes is using these guidelines and going through some biochemistry, and you will be well on your way to mastering the art of naming enzymes without having to memorize a single thing!

To your success!

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