Can you tell from the name if an enzyme degrades?

[sniderwes]

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It seems like most enzymes on the MCAT catalyze degradation reactions, ex: lipase degrades lipids, acetylcholinesterase degrades acetylcholine.

So when you're given the name of an enzyme on the MCAT (of the form substrate'ase) is there a way to tell if it degrades the substrate or if it just speeds up a nondegrative reaction?

 

[premed1001]

My understanding was that most enzymes can function in the reverse reaction as well, usually as a condition of PH? Not entirely sure about this tho

 

[Czarcasm]

Yes. All enzymes usually end with -ase. There are 6 general classes based on the reactions they catalyze:

Oxidoreductase: Catalyzes oxidation-reduction reaction (gains or loses oxygen or hydrogen)
Transferase: Transfers functional groups (for ex. amino group, acetyl group, or phosphate group)
Hydrolase: Hydrolysis (addition of water)
Lyase: Removes atoms without water (no hydrolysis)
Isomerase: Re-arranges atoms within a molecule
Ligase: Joins molecules together (anabolic reactions) which are usually coupled to the favorable breakdown of ATP

So while these are the general classes of enzymes, sometimes names can be even more specific within a given classification:

Cytochrome oxidase (Oxidoreductase)
Acetate Kinase (Transferase)
Alanine Deaminase (Transferase)
Lipase (Hydrolase)
Sucrase (Hydrolase)
Isocitrate Lyase (Lyase)
Oxalate decarboxylase (Lyase)
Glucose-phosphate Isomerase (Isomerase)
Alanine racemase (Isomerase)
DNA Ligase (Ligase)
Acetyl-CoA Synthetase (Ligase)

So as you can see, you can deduce some of the functions for some of these most of the time just by analyzing the names of each enzyme. It helps a ton 🙂

 

[Czarcasm]

My understanding was that most enzymes can function in the reverse reaction as well, usually as a condition of PH? Not entirely sure about this tho

While that's true, it's important to keep in mind that enzymes are only useful for speeding up spontaneous reactions. Assuming the reaction you are considering is spontaneous, the reverse reaction is non-sponanteous and therefore not favorable. In this case, even in the presence of the catalyst, the reaction could take ages to occur.

Think about a sheet of paper which can ignite into a flame. If you left the paper out in the sun, chances are it would take ages before it accumulated enough free energy to ignite. Let's say we added a catalyst to speed up the reaction -- we pour some gasoline on the paper. If a fire were present, it would certainly burn faster, but regardless, there's still not enough energy for the reaction to occur -- so considering the gas (or enzyme) is essentially useless.

 

[DrknoSDN]

It seems like most enzymes on the MCAT catalyze degradation reactions, ex: lipase degrades lipids, acetylcholinesterase degrades acetylcholine.

So when you're given the name of an enzyme on the MCAT (of the form substrate'ase) is there a way to tell if it degrades the substrate or if it just speeds up a nondegrative reaction?

Czarcasm is right, you just gotta memorize the important enzymes and learn to recognize the names of the rest. I can't think of any hard rule for enzyme nomenclature.

And for MCAT purposes, yes enzymes catalyze both the forward and reverse reaction but reversal is usually very unlikely from an energy-thermodynamics standpoint.