Monday, July 23, 2012

Monday's Molecule #178

It's the dog days (dies caniculares) of summer and Sirius is hard at work.

I'm going to let you off easy today. Identify the four molecules whose structures are shown on the right and name the two enzymes that catalyze the reactions. For extra accolades, tell us why those two enzymes are important in evolution and why the blogosphere is currently talking about these kinds of enzymes.

Post your answer as a comment. I'll hold off releasing any comments for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch with a very famous person, or me.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your comment.)

Some past winners are from distant lands so their chances of taking up my offer of a free lunch are slim. (That's why I can afford to do this!)

In order to win you must post your correct name. Anonymous and pseudoanonymous commenters can't win the free lunch.

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Comments are invisible for 24 hours.

Nov. 2009: Jason Oakley, Alex Ling
Oct. 17: Bill Chaney, Roger Fan
Oct. 24: DK
Oct. 31: Joseph C. Somody
Nov. 7: Jason Oakley
Nov. 15: Thomas Ferraro, Vipulan Vigneswaran
Nov. 21: Vipulan Vigneswaran (honorary mention to Raul A. Félix de Sousa)
Nov. 28: Philip Rodger
Dec. 5: 凌嘉誠 (Alex Ling)
Dec. 12: Bill Chaney
Dec. 19: Joseph C. Somody
Jan. 9: Dima Klenchin
Jan. 23: David Schuller
Jan. 30: Peter Monaghan
Feb. 7: Thomas Ferraro, Charles Motraghi
Feb. 13: Joseph C. Somody
March 5: Albi Celaj
March 12: Bill Chaney, Raul A. Félix de Sousa
March 19: no winner
March 26: John Runnels, Raul A. Félix de Sousa
April 2: Sean Ridout
April 9: no winner
April 16: Raul A. Félix de Sousa
April 23: Dima Klenchin, Deena Allan
April 30: Sean Ridout
May 7: Matt McFarlane
May 14: no winner
May 21: no winner
May 29: Mike Hamilton, Dmitri Tchigvintsev
June 4: Bill Chaney, Matt McFarlane
June 18: Raul A. Félix de Sousa
June 25: Raul A. Félix de Sousa
July 2: Raul A. Félix de Sousa
July 16: Sean Ridout, William Grecia


  1. Raul A. Félix de SousaMonday, July 23, 2012 7:04:00 PM

    Molecule # 178
    First line shows the interconversion of Lactate and Pyruvate, which is catalysed by Lactate dehydrogenase.
    Second line shows the interconversion of Malate and Oxaloacetate, which is catalysed by Malate dehydrogenase.
    These reactions occur in all organisms and the structures of these enzymes contain valuable information about the early evolution of the three domains of life.

  2. Lactate and pyruvate on top (lactate dehydrogenase) and malate and oxaloacetate on bottom (malate dehydrogenase).

  3. Lactate to pyruvate, enzyme Lactate Dehydrogenase (LDH)

    Malate to oxaloaceteate, enzyme Malate Dehydrogenase

    Both enzymes are Krebs cycle enzymes need to fuel oxidative phosphorylation. This enabled bacteria to utilize previously toxic oxygen to achieve high energy efficiency. Bacteria of this type formed a symbiosis with other cells transforming into mitochondria as part of the emergence of eukaryotes.

  4. The first reaction is lactate going to pyurvate, catalyzed by lactate dehydrogenase.

    The second reaction is malate going to oxaloacetate, catalyzed by malate dehydrogenase.

    I'm not sure of recent blogs, but sequence changes both enzymes have been analyzed in evolutionary studies. They have similar 3-D structures and catalytic mechanisms, and lactate dehydrogenase can be converted to a malate dehydrogenase by a single amino acid substitution (the reverse change in malate dehydrogenase does not change it to a lacate dehyrogenase activity).