13 - Friday Lecture 13 Announcements 1 Quiz 3 results a...

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Friday, September 24, 2010, Lecture 13 Announcements: 1. Quiz 3 results: a 25.2 b 27.2 c 25.4 2. Meet today at 2:55PM in Comstock B108: “Applying to graduate school-- what are they looking for?" Wednesday's lecture: Ion pairs stabilize the structure of deoxy-Hb. These are “potential” ion pairs, and by use of the Henderson-Hasselbalch equation, the fraction actually in an ion pair can be calculated. Quarternary structure (IV) of Hb can be in two states, R (relaxed) or T (tense) Bohr effect, fetal Hb getting oxygen from the mother, these are explained by ion pairs stabilizing the T-State Two models can explain Hb behavior: the Sequential Model and the 2-State Model. Today: ENZYMES LG p. 97 is a more clear and detailed version of Table 6-3 in your text. The 6 classes of enzymes describe ALL enzymes (!). 1 . Oxidoreductases: in the second column, you see EC1.1.1.1. EC stands for Enzyme Commission, the official organization that classifies enzymes. Each number after “EC” has a different meaning. The first number informs as to which of the 6 enzyme classes the enzyme belongs. A 1 means the enzyme is an oxidoreductase. In case this is useful for you (e.g. hunting for a particular enzyme), the web site that has the latest official nomenclature is: http://www.chem.qmul.ac.uk/iubmb/enzyme/index.html The second “1” means it uses a C-OH as electron donor. The third “1” means that NAD + or NADP + is the electron acceptor. (1.1.2 means a cytochrome is the electron acceptor; 1.1.3 means oxygen is the electron acceptor) The last “1” indicates substrate specificity, i.e. the specific enzyme 2 . Transferases: These enzymes catalyze the transfer or functional groups. 2.7 means a transfer of a phosphate. 2.7.1 means an -OH is accepting the phosphate. (So, 2.7.1 is a general description for kinases) 2.7.1 .2 indicates the last level of substrate specificity, for glucose
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3 . Hydrolases: These enzymes add water across a bond. Also in this category are the membrane transporters! For example: 3.6 means “acting on acid anhydride” with 3.6.4 acting on ATP, 3.6.5 acting on GTP, and 3.6.3 acting on ATP or GTP and causing transmembrane movement of another molecule. Carboxypeptidase and trypsin are also examples of hydrolases. 4 . Lyases: These enzymes catalyze the removal or addition of a “group” usually at double bonded atoms, such as at C=C, or C=O, or C=N (but hydrolysis is not involved in the rxn) . 5 . Isomerases: These enzymes catalyze intramolecular rearrangement. 6 . Ligases: These enzymes catalyze the joining of two molecules, usually coupled to ATP cleavage. These enzymes can form or break the bonds: C-O, C-C, C-S, and C-N. **For this course, you will NOT need to know the systematic naming system (no
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This note was uploaded on 12/10/2011 for the course BCHEM 3350 taught by Professor Feig during the Fall '09 term at Cornell.

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13 - Friday Lecture 13 Announcements 1 Quiz 3 results a...

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