Amino Acids, Proteins and Porphyrins
An 80-year-old man presented with impairment of higher intellectual function and alterations in mood and behavior. His family reported progressive disorientation and memory loss over the last six months. There is no family history of dementia. The patient was tentatively diagnosed with Alzheimer disease. Which one of the following best describes the disease?
|A||It is associated with β-amyloid—an abnormal protein with an altered amino acid sequence.|
|B||It results from accumulation of denatured proteins that have random conformations.|
|C||It is associated with the accumulation of amyloid precursor protein.|
|D||It is associated with the deposition of neurotoxic amyloid peptide aggregates.|
|E||It is an environmentally produced disease not influenced by the genetics of the individual.|
a. Alzheimer disease is associated with long, fibrillar protein assemblies consisting of beta-pleated sheets found in the brain and elsewhere. The disease is associated with abnormal processing of a normal protein.
b. The accumulated altered protein occurs in a β-pleated sheet configuration that is neurotoxic.
c. The Aβ amyloid that is deposited in the brain in Alzheimer disease is derived by proteolytic cleavages from the larger amyloid precursor protein—a single transmembrane protein expressed on the cell surface in the brain and other tissues.
d. Most cases of Alzheimer disease are sporadic, although at least five to ten percent of cases are familial.