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In Life Ascending the author, Nick Lane, refers to an enzyme in his introduction:

'' It concerns an enzyme (a protein that catalyses a chemical reaction) that is so central to life that it is found in all living organisms, from bacteria to man. This enzyme has been compared in two different species of bacteria, one living in superhot hydrothermal vents, the other in the frozen Antarctic. The gene sequences that encode these enzymes are different; they have diverged to the point that they are now quite distinct. We know that they did diverge from a common ancestor, for we see a spectrum of intermediates in bacteria living in more temperate conditions. But from the gene sequences alone there is little more we can say. They diverged, surely because their living conditions are so different, but this is abstract theoretical knowledge, dry and two-dimensional. But now look at the molecular structure of these two enzymes, pierced by an intense beam of X-rays and deciphered through the wonderful advances in crystallography. The two structures are superimposable, so similar to each other that each fold and crevice, each niche and protrusion, is faithfully replicated in the other, in all three dimensions. An untutored eye could not distinguish between them.....The building blocks bind tightly to each other, through internal bonds that work like cement, retaining the structure despite the buffeting of energy from the boiling vents..... In the ice, the picture is reversed. Now the building blocks are flexible, allowing movement despite the frost...... Compare their activity at 6°C, and the frosty enzyme is twenty-nine times as fast; but try at 100°C, and it falls to pieces. The picture that emerges is colourful and three-dimensional. The changes in gene sequence now have meaning: they preserve the structure of the enzyme and its function, despite the need to operate under totally different conditions.''

Emphasis mine and .... indicates omitted text.

I would be very grateful if anyone could tell me what this enzyme is, and if possible point me to further information about it!

N. B. the enzyme is only mentioned in the introduction "... never found the opportunity for a mention in the book proper." There are no references for said introduction, only the chapters.

Thank you!

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    $\begingroup$ I'm not sure it'll be possible, since he doesn't provide any details in the book. There are a lot of enzymes with highly conserved structures, so it'll be hard to figure out which one he's specifically referring to here $\endgroup$
    – divibisan
    Dec 21, 2018 at 18:42
  • $\begingroup$ This is conserved structure but totally distinct gene sequence, is that also so common? If so could you please give me a pointer to one of particular interest? I can probably read from there outwards till I have satisfied my curiosity. $\endgroup$
    – Mirte
    Dec 21, 2018 at 18:45
  • $\begingroup$ @Mirte It doesn't say totally distinct, it says "they are now quite distinct"; "quite" is of course an imprecise word but I wouldn't say it means "totally", and the passage also refers to intermediates that would be intermediately distinct from each. It is not surprising that an enzyme would evolve similar structure to catalyze the same reaction at different temperatures, and that keeping this structure would require a different sequence of amino acids. As divibisan suggests, without further information from the author they could be referring to many enzymes. $\endgroup$
    – Bryan Krause ♦
    Dec 21, 2018 at 19:15
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    $\begingroup$ Note the second snippet from the book link user1136 provided gives a revised version of the first sentence which OP quotes, to wit: It concerns a protein (a catalyst, or enzyme, called citrate synthase) that is so central to life that it is found in all living organisms, from bacteria to man. $\endgroup$
    – mgkrebbs
    Dec 22, 2018 at 1:41
  • $\begingroup$ @user1136 I'll vote for your answer if you write one :-) $\endgroup$
    – Mirte
    Dec 22, 2018 at 9:10

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