Tal­mu­dic Ques­tion #108

This is a per­fect ex­am­ple of a Tal­mu­dic Ques­tion, Elio! When I teach in­tro­duc­tory bio­chem­istry, I of­ten get the "so why does the en­zyme do it that way?" kind of ques­tion. Why does Ru­bisco mis­take car­bon diox­ide for oxy­gen? What does triose phos­phate iso­merase pro­duce 96% DHAP (which is not us­able, and can be toxic) to 4% GA3P at equi­lib­rium (though to be fair, that lat­ter ex­am­ple is a good il­lus­tra­tion and re­minder that *life* is not at equi­lib­rium)?
I some­times re­ply that these are more the­o­log­i­cal than bio­chem­i­cal ques­tions. It's not al­ways a sat­is­fy­ing an­swer, sort of like "what con­trols tran­scrip­tion fac­tors" be­ing an­swered by "other tran­scrip­tion fac­tors."
Get­ting back to cel­lu­lose, I ham­mer on my fresh­man to con­sider the "shape" of lig­ands and bonds—I call it a made up word, "stericity"—are cen­tral to all of bi­ol­ogy. So the beta 1->4 glu­co­sidic bonds are not well rec­og­nized by eu­kary­otic hy­dro­lases? And it ap­pears that mi­crobes and mac­robes look at this as a meta­bolic prob­lem with a "crowd­sourced" so­lu­tion (as ob­served in the mi­cro­bial uni­verse within a mil­li­liter of ru­men fluid, to bor­row from William Blake).
Great op­por­tu­ni­ties for class­room dis­cus­sion, in any event. I am go­ing to pick and choose among your Tal­mu­dic Ques­tions and make it a weekly fea­ture in my Fall mi­cro­bi­ol­ogy course (and I still think the col­lec­tion would make one heck of a book!).
Thanks again, Mark Mar­tin