Friday, November 14, 2014

Cartoon Versions of Glycolytic Enzymes - Part I

Cross-posted from my Tumblr

Someone on Tumblr asked for help understanding glycolysis (along with a lot of other things, but I decided to focus on glycolysis first), so I had the brainwave of drawing cartoon versions of all the glycolytic enzymes.

Here are my cartoon interpretations of the enzymes catalyzing the first five steps of glycolysis:

1. Hexokinase
Hexokinase, drawn as a pair of interlocking jaws with a space for glucose and ATP
I drew this one to look like a huge snapping alligator jaw that fits together like a jigsaw puzzle, except for a small space near the back for glucose and ATP to fit into. (See the links at the bottom of this post, and also this blog -- particularly this post -- for more realistic images of hexokinase).

2. Phosphoglucose isomerase
Phosphoglucose isomerase, drawn as a stylized pair of interlocking hands
I have functional as well as structural reasons for choosing this way to represent this enzyme; besides the fact that its structure really is two identical subunits shaped roughly like twin blobs with long arms wrapped around one another — arms that remind me of thumbs sticking out from fists — I also figured that, since its function is to break the ring that makes up glucose, change a few things around and then let the ring re-form into fructose, a pair of hands looks like something that could do that. Like I drew hexokinase — whose function is to clamp itself around glucose — as a pair of jaws, I drew this one thinking to evoke some everyday-life analogy for what it does. The analogy that occurred to me was cracking an egg, which I do with two hands, using my thumbs to pry the shell open. (See the links at the bottom of this post, plus this one*, this one, and this one, for more realistic images of phosphoglucose isomerase).

3. Phosphofructokinase
Phosphofructokinase, drawn as a pinwheel with a smiley face in the middle
I drew a pinwheel to represent phosphofructokinase. I chose that shape because most of the drawings and computer models I found of its structure seemed to show a radial symmetry, of either 90 or 180 degrees depending on which image I was looking at. (See the links at the bottom of this post, plus this one, this one, this one and this one, for more realistic images of phosphofructokinase).

4. Aldolase
Aldolase, drawn as a pair of butterfly wings
I chose a butterfly for aldolase because in most of the drawings and computer models I could find of its structure, it looked like it had mirror symmetry. (See the links at the bottom of this post, plus this one and this one***, for more realistic pictures of aldolase).

5. Triose phosphate isomerase
Triose phosphate isomerase, drawn as a barrel with a face
I drew this one as a barrel, to reflect the "beta barrel" that makes up its interior structure, and contains the active site. (See the links at the bottom of this post, plus this one, this one and this entire blog -- particularly this post -- for more realistic images of triose phosphate isomerase). 

As you can hopefully see if you've been clicking on the links, I've tried to anchor all of my cartoon avatars of these enzymes in some element of their actual structure.

Here are some general links where you can see some decent representations of the structures of all ten of these enzymes:

Glycolysis (enzymes of the preparatory phase)

Glycolysis (enzymes of the payoff phase)

The Glycolytic Enzymes (PDF)


*The linked image is an illustration from an evolutionary biology textbook -- Evolution, by Nicholas H. Barton, Derek E. G. Briggs, Jonathan A. Eisen, David B. Goldstein, and Nipam H. Patel. The book has a website, where you can see some of the content -- including all the illustrations -- for free. 

This particular image is not original, though -- the ultimate source is a paper from 2006 by Christopher W. Wheat, Ward B. Watt, David D. Pollock and Patricia M. Schulte. It was published in Molecular Biology and Evolution and you can read the full text here.

**The linked image is Figure 2 from this article in Biochemical Society Transactions


Mitternacht, S., and Berezovsky, I. (2011). Coherent Conformational Degrees of Freedom as a Structural Basis for Allosteric Communication PLoS Computational Biology, 7 (12) DOI: 10.1371/journal.pcbi.1002301

Perica, T., Marsh, J., Sousa, F., Natan, E., Colwell, L., Ahnert, S., and Teichmann, S. (2012). The emergence of protein complexes: quaternary structure, dynamics and allostery Biochemical Society Transactions, 40 (3), 475-491 DOI: 10.1042/BST20120056

Wheat, C. (2005). From DNA to Fitness Differences: Sequences and Structures of Adaptive Variants of Colias Phosphoglucose Isomerase (PGI) Molecular Biology and Evolution, 23 (3), 499-512 DOI: 10.1093/molbev/msj062

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