Let us turn now to the One True God of science and atheism, the Ground State of our existence. We shall now contemplate Caffeine. Raise your cup in praise.
This morning, as I was sipping the blessed stimulant and browsing the journals, I learned a little something. I learned how caffeine evolved, and it was both unsurprising and surprising. I am not a biochemist, so it’s always enlightening to read a little out of that field. This, for instance, is the chemical precursor in the synthesis of caffeine.
Oh, I said, I certainly do recognize that — I’ve been teaching budding cell biologists about important biological macromolecules for the past few weeks, and that’s a nucleoside. Note the ribose sugar with the attached nitrogenous base, the double ring of one pentagon attached to a hexagon? That’s xanthosine, which is also a precursor in the synthesis of those purines our cells use in signaling and assembling chains of nucleotides in DNA and RNA. That’s obvious. And then you look at caffeine, and it’s also obvious how cells make it: slap a couple of methyl groups (those -CH3s sprinkled around), and presto, you’ve got a happy drug. Easy.
Except…not all cells make significant amounts of caffeine. It takes specific enzymes to glue those methyl groups onto the core base with any reliable yield, and my cells might have xanthosine around, but they aren’t making any for me. I have to raid the vegetable kingdom and tear off their leaves and beans and hit them with boiling water to extract the blessed caffeine. And then not all plants make it — I can’t get a buzz on with a bowl of peas in the morning.
And then I learn that caffeine has evolved independently at least 5 times, and that the distribution of caffeine is patchy — some species in a genus will make it, while other related species in the same genus don’t. The caffeine molecule in Coffea (coffee) and Camellia (tea) and Theobroma is identical, but it’s synthesized by different pathways.
My mind is blown. Excuse me, but I have to take a break and think about this. I’m going to take a walk down to the coffee shop and gurgle down a couple of cups to help absorb this information. I’ll resume this post a little later.
You understand, don’t you? Go have another cup of coffee or tea while you’re waiting.