Vital Dust: Life as a Cosmic Imperative

By Christian De Duve | Go to book overview
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Chapter 2
The First Catalysts of Life

FROM THE FIRST building blocks of life well into the RNA world. Such is the hidden trail we must try to uncover. We know the outcome: complex organic substances made of carbon, nitrogen, oxygen, hydrogen, and phosphorus atoms linked with each other in molecular structures that are known with great accuracy. Our task is to find out how such arrangements arose naturally from simpler arrangements of the same atoms present in the prebiotic environment. Our major clue comes from the requirement for congruence. The metabolic maps reproduced in all biochemistry textbooks are modernized versions of the ancient networks and should help us in our task.

Enzymes are the signposts on metabolic maps. Virtually every one of the thousands of chemical reactions that take place in any living cell is catalyzed by an enzyme. Most of these reactions would not occur at all without enzymes. Hundreds of fatal or severely disabling genetic diseases characterized by a single enzyme deficiency attest to this fact. It is very unlikely that protometabolism could have done without catalysts. If these were not proteins, what were they?


CATALYSIS WITHOUT PROTEINS

Just as metabolism cannot operate without enzymes, protometabolism, whatever pathways it may have followed, could not have functioned without catalysts. Textbooks define catalysts as substances that specifically help reacting molecules to get together and interact, but are not themselves consumed in the reaction and, therefore, can serve an indefinite number of times in succession. Why did emerging life need catalysts? Chemical reactions take place all the time in the physical world without the help of catalysts.

There are two reasons for the requirement for catalysts: rapidity and yield. Uncatalyzed reactions most often are very slow. This means, in the prebiotic set

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