Really Awesome Proteins: Transketolase

This is a regular feature that has been carried over from my previous blog, the Really Awesome Protein (RAP) series. This does not mean I’m going to attempt to spread the protein love via ghetto-speak, gangster rhymes and poor beat boxing, although I am totally up for trying that. Actually it just means that once a fortnight or so I am going to try and convince you that the molecules in your body are as exciting, mind-blowing, awe-inspiring, and amazing as anything out there in the cosmos. This series is to be a celebration of some of the most stunningly beautiful and phenomenally clever molecules in nature.

The first RAP in my new home just has to be the protein that my online nickname stemmed from, transketolase. During my biochemistry degree I wrote an essay on this protein and my Dad, a man who lives for terrible word-play, noted that the name could be very easily altered to sound like my name, i.e., transkatielase. My extremely nerdy best friend lit upon this as a nickname, and Katielase was born. So, since I owe my online identity as an over-excitable science nerd to this protein, I owe it to you all to explain just exactly what it is I’d do, if I were a protein.

(At this point I must say, it would have been handy if I had saved the text from the massive essay I did write on this protein in my second year, although in that essay there were far fewer references to cake and a lot less nonsensical rambling.)

No-one notices the co-factors

Many reactions in your body require co-factors; these are non-protein molecules that attach themselves to enzymes, thus allowing them to work. Co-factors are unassuming molecular facilitators; they are Alfred the Butler to the enzyme Batman; they just want to help your proteins out, recognition is not important. One of the co-enzymes in biochemistry is NADPH, which is particularly crucial for the production of fatty acids and lipids in your cells. It is also involved in producing free radicals, which are used by your immune system to kill invading pathogens.

Cofactors, the Alfred the Butlers of the molecular world.

NADPH is generated as a product of the pentose phosphate pathway, which is where transketolase comes in. Transketolase catalyses two reaction in the pentose phosphate pathway, and therefore is essential to the production of NADPH in your cells. And without NADPH… well Batman has no Batmobile. Your immune cells can’t produce free radicals to zap pathogens with, and your cells can’t produce lipids. You’re not doing well, trust me.

The first job of transketolase in the pentose phosphate pathway is to take two molecules, D-xylulose-5-phopshate and D-ribose-5-phosphate, and transform them, via a nifty bit of carbon reassigning, into two new molecules, sedoheptulose-7-phosphate and glyceraldehyde-3-phosphate. These can then be used for the next stage of the pathway. And, as I said, this pathway is crucial for producing NADPH, an unassuming Alfred the Butler-like co-factor of your cells.

And Treasurer of The Co-Factor Appreciation Society isn’t the only thing transketolase is good for…

Give me some sugar

The process of using sweet sugary glucose to create the energy currency of the cell, ATP, is known as glycolysis. It’s a step-by-step pathway that takes the glucose sugar from the cake you ate, and transforms it into pyruvate, generating a mini motherload of ATP along the way. ATP is  then used to do… almost everything in the cell that requires a source of energy; active transport of molecules around the place, the production of DNA, RNA and proteins, cell signalling, without ATP we would basically all be dead.

During its second starring role in the pentose phosphate pathway, transketolase once again produces glyceraldehyde 3-phosphate, only this time it also produces fructose 6-phosphate. Fructose-6-phosphate is an excess phosphate sugar, it isn’t required as part of the phosphate pathway, instead it is fed into the glycolysis system, to sacrifice itself for the production of ATP. To KEEP YOU ALIVE. Scientific melodrama at its best, there.

Beautiful transketolase. Keeping you alive, melodramatically.
Image credit.

So, that’s transketolase. On the one hand, a relatively average enzyme, nothing special, not well-known, but on the other hand, one of many many enzymes that keep you alive, as part of the beautiful complex biochemical system of your cells. And, of course not forgetting, the origin of a clearly hilarious online nerd-name, an equally important and relevant achievement.