Studies conducted with a lysozyme mutant that contains an Asp->Asn change at position 52 and a Glu->Gln change at position 35 exhibited almost a complete loss in enzymatic activity
What is the most likely explanation for the decrease in enzyme activity in the mutant?
(a) increased affinity for substrate
(b) absence of negative charges in the active site
(c) change in the active-site scaffold
(d) larger amino acids in the active site decreases the affinity for substrate
(b) The negatively charged amino acids aspartic acid and glutamic acid are required to attack the sugar bonds being cleaved by lysozyme. Replacing these with side chains that are the same length and are polar, but uncharged, would most probably affect only the catalysis, not the binding of substrate or the stability of the protein.
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The organism that causes malaria is
(a) a pathogen. (b) Plasmodium vivax. (c) carried by a mosquito. (d) all of the above.
Why does natural selection favor organisms that are benthic in estuaries? a. Changes in salinity
b. The constant movement of water. c. Changes in temperature. d. The high amount of nutrients.
The main regulator of calcium blood levels is
a. the parathyroid glands. b. the thyroid glands. c. the hypothalamus. d. the anterior pituitary gland. e. the posterior pituitary gland
Refer to Figure 40-3. In which portion of the bone would red blood cell production occur?
a. B b. C c. J d. H e. I