In Today's New Reason to Believe e-mail sent out by the Reasons to Believe organization. They state the following:

New work on the characteristics of an enzyme that plays a key role in photosynthesis provides an effective response to one of the most compelling arguments for evolution. Biologists point to seemingly faulty designs in nature as evidence for evolution. One widely recognized example of a "poor" biochemical design is the enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase, which plays a key role in photosynthesis. This enzyme (which converts carbon dioxide and ribulose 1,5-bisphosphate into two 3-carbon sugars that eventually yield glucose) works at an extremely slow rate and is readily confused by the presence of oxygen. The biochemical confusion results because carbon dioxide and oxygen are featureless molecules that are difficult to tell apart. However, scientists have found that by slowing down the rate of chemical conversion, the enzyme is able to discriminate between carbon dioxide and oxygen. Thus, the enzyme appears to be perfectly optimized to handle carbon dioxide binding in the presence of oxygen. This classic example of a biochemical imperfection is now recognized as an elegantly designed system.

Here's a link to the article they refer to.

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NOTE: I have disabled comments on this and all future articles because I am being deluged with spam.

UPDATE: Since moving over to Movable Type, I have reinstated comments. Hopefully, I won't get any spam.