Dear Miss Metabolism...

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Dear Miss Metabolism,

I don't know what to do with myself, I'm so lonely. I used to be carbon atoms 4, 5 and 6 of a happy fructose-1,6-bisphosphate compound, but I guess I forgot how lucky I was, got restless, and decided I wanted us to split up.

I had seen so many of my friends going off into glycolysis and it looked like fun, and I was curious. I had no idea what a big mistake I was making, but I told my other half I wanted a trial separation, and here I am.

We found an aldolase enzyme, it wasn't hard, there was practically one on every street corner, and she promised us that it would just be a reversible reaction, that we could get back together whenever we wanted. Technically, I guess she was telling the truth. Except that after I became a dihydroxyacetone phosphate, I never saw my glyceraldehyde 3-phosphate again.

I guess I thought she would wait for me to get it out of my system, but she didn't. She rushed off into glycolysis, maybe she was feeling hurt, and left me all alone. Glyceraldehyde-3-P dehyrogenase enzymes won't even look at me, so I'm just stuck here.


Please Miss Metabolism, I'm just a foolish intermediate who didn't know how good I had it, please tell me what I should do now?


Yours,
Sad in the Cytosol



Dear Sad in the Cytosol,

Don't be too hard on yourself, you weren't to know this, but those aldolase enzymes are a bunch of home-wreckers! They always say the separation is temporary, that you can both reconcile later if you find you're unhappy, but most of the time, the two compounds just get completely broken down in to carbon dioxide and float away. It's hard being single.

Listen, chances are, your darling GAP is long-gone. All you can do now is remember the good times, and get on with your metabolism. Basically, you have three main options:

1. Mind the GAP. Finding another glyceraldehyde-3-P to settle down with might be difficult, but if you are in a cell that's doing gluconeogenesis, it's not such a long shot.



2. Get fat. Why not try an alternative metabolic lifestyle, and get reduced to a glycerol-3-P. You could settle down with some nice fatty acids (not hard on today's modern 'diets'), and live the quiet life of a triacylglycerol molecule, or the fast-paced career of a phospholipid.



3. Switch teams. If life alone really is that unbearable, why not find a triose phosphate isomerase and become a GAP yourself. Maybe by following your ex's footsteps, you might even get some closure. Be careful though, if you go all the way to becoming an acetyl CoA, you will have given up on life as a carbohydrate forever.

So think carefully before you make your decision, even reversible reactions can have irreversible consequences.

Dynamically yours,
Miss Metabolism