2Alecture+8

S s note this axis is not me note also in these

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Unformatted text preview: /10 Adjuncts to protein catalysts (aka prosthe>c groups, cofactors) (note similari>es to mineral catalysts) 1. 2.  3.  4.  Three types of protein iron-sulfur clusters (here’s one- a 4Fe-4S cluster) cysteine Metals  ­ ­ Zinc, Magnesium, Iron, Manganese Iron ­sulfur clusters Metal ­binding cofactors ­ ­ heme, chlorophyll “Coenzymes” ­ many vitamins, also our old friends NAD, FAD, and ATP cysteine cysteine Like the protein part of the enzyme, these cofactors come out of the reac>on unscathed. They are catalysts, not substrates. Ferredoxin- an electron carrier Note how enzymes resemble mineral surfaces, in a new matrix. 1FXR Many of the minerals and cofactors critical for catalysis may also be clues to how catalysis arose -- Perhaps originally simple minerals were catalysts Some co-factors may have been adaptors that enhance or restrict this catalytic activity Amino acids (and later proteins) could be new developments that enhance specificity for particular substrates. Without a catalyst- Rate (v) is rate constant (k) x [S] = k[S] How can you measure how an enzyme works? The substrates(s) have to bind to the catalytic surface. So the rate of a reaction could be limited by the availability of active sites. But with a catalyst, this isn’t true at high substrate concentration… Why does the rate flatten out? [S] [S] (note this axis is not >me) Note also, in these discussions we’re talking about a specific experiment setup We measure initial reaction rate in a reaction that has on...
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This note was uploaded on 06/13/2013 for the course BIS 2A taught by Professor Grossberg during the Winter '08 term at UC Davis.

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