Use the following information for the first 6 questions. Lactate dehydrogenase (

Question

Use the following information for the first 6 questions. Lactate dehydrogenase (LDH), can reduce pyruvate, forming lactate, or oxidize lactate, forming pyruvate. Illustrated here is the structure of a bacterial LDH called PaLDH. PaLDH has 4 identical subunits. Each quadrant in the image represents essentially one subunit. The "P" axis shows interactions between the top (A or D) and bottom (B and C) subunits. The space-filling section of each quadrant shows the active site of each subunit. Assume the arrows in the ribbon diagram are all pointing in the SAME direction. The Hill coefficient for PaLDH with pyruvate is approximately 0.5 B- 1. Since the arrows are pointing in the SAME direction, PaLDH has: a. Parallel sheets. b. Antiparallel sheets 2. The tertiary structure of PaLDH is best described as: a. The globin fold b. All beta (B) c. A mixture of alpha (a) and beta (B) d. A TIM barrel. e. The 3-10 helix The quaternary structure of PaLDH is best described as a: a. Homodimer. b. Heterodimer. c. Heterotetramer. d. Homotetramer. e. Monomer. 3.

Explanation / Answer

Please find the answers below:

Answer 1: Choice a (parallel sheets run in same direction whereas anti-parallel sheets have opposite polarity and run in opposite direction)

Answer 2: Choice c (as clearly demonstrated in the image and the information description, the enzyme assumes a tertiary structure mixture of alpha and beta structures)

Answer 3: Choice c (since the enzyme contains 4 distinct structural subunits, it assumes a hetero (different) tetramer (four) structure.)

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