Question

Read "Malate dehydrogenase: A model for structure, evolution, and catalysis"

1. Looking at Figure 1, to which form of MDH is LDH most closely related? Give your reasoning in each case:

a. cytoplasmic MDH or archaeal MDH

b. mitochondrial MDH or cytoplasmic MDH

2. The sequences of MDH from various organisms aren't very similar, however their structures are very similar. List 3 characteristics of their structures that are conserved:

a.

b.

c.

3. What suggests that MDH and LDH use a similar catalytic mechanism?

4. What accounts for the differences in substrate specificity between MDH (malate is the substrate) and LDH (lactate is the substrate)?

Answer 1

1. a. archeal MDH are related to LDH because this group has greater amino acid sequence identity with each other.

b. mitrochondrial MDH and LDH are used in the synthesis of glucose.

2. a. they are homodimeric molecules.

b.interacting alpha-helices that fit compactly together

c.the core dinucleotide binding structure is composed of 4 beta-sheets and one alpha-helices

3. the co-enyzmes are similar and the structure.

4. the active sites