Biological reactions take 2.4 billion years - minus enzymes

November 11th, 2008 - 3:26 pm ICT by IANS  

Washington, Nov 11 (IANS) Biological reactions that occur in the blink of an eye within cells, thanks to enzymes or catalysts, would take 2.4 billion years otherwise!”This enzyme is essential for both plant and animal life on the planet,” said Richard Wolfenden, professor and biochemist at the University of North Carolina (UNC).

“What we’re defining here is what evolution had to overcome, that the enzyme is surmounting a tremendous obstacle.”

He had reported in 1995 that sans a particular enzyme, a biological transformation he deemed “absolutely essential” in creating DNA, RNA building blocks, would take 78 million years.

“Now we’ve found a reaction that - again, in the absence of an enzyme - is almost 30 times slower than that,” Wolfenden said.

“Its half-life - the time it takes for half the substance to be consumed - is 2.3 billion years, about half the age of the earth. Enzymes can make that reaction happen in milliseconds.”

“Without catalysts, there would be no life at all, from microbes to humans,” he said. “It makes you wonder how natural selection operated in such a way as to produce a protein that got off the ground as a primitive catalyst for such an extraordinarily slow reaction.”

“Enzymes that do a prodigious job of catalysis are, hands-down, the most sensitive targets for drug development,” Wolfenden said. “The enzymes we study are fascinating because they exceed all other known enzymes in their power as catalysts.”

The reaction in question is essential for the biosynthesis of haemoglobin and chlorophyll, Wolfenden noted.

When catalysed by the enzyme uroporphyrinogen decarboxylase, the rate of chlorophyll and haemoglobin production in cells “is increased by a staggering factor, one that’s equivalent to the difference between the diametre of a bacterial cell and the distance from the Earth to the sun”, he said.

Wolfenden has carried out extensive research on enzyme mechanisms and water affinities of biological compound, according to an UNC release.

His work has also influenced rational drug design, and findings from his lab spurred development of ACE inhibitor drugs, widely used to treat hypertension and stroke.

Research on enzymes as proficient catalysts also led to the design of protease inhibitors that are used to treat HIV infection.

“We’ve only begun to understand how to speed up reactions with chemical catalysts, and no one has even come within shouting distance of producing, or predicting the magnitude of, their catalytic power,” Wolfenden said.

With co-author Charles A. Lewis, Wolfenden published a report recently in the online early edition of the Proceedings of the National Academy of Science. The study also appeared on Tuesday in its print edition.

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