【简答题】第二节:读写任务(共1小题,满分25分) 阅读下面的短文,然后按照要求写一篇150词左右的英语短文。 “In addition to teaching here, I also teach at a smaller high school 17 miles down the freeway from where I live. One day a few weeks ago I was drivi...
【多选题】In addition to electron t ransfer, NAD has other important functions:
A.
Some key cellular functions are regulated by enzymes that use NAD + not as a redox cofactor but as a substrate in a coupled reaction in which the availability of NAD + can be an indicator of the cell’s energy status.
B.
A family of proteins called sirtuins regulate the activity of proteins in diverse cellular pathways by deacetylating the ε-amino group of an acetylated Lys residue. The deacetylation is coupled to NAD + hydrolysis, yielding O -acetyl-ADPribose and nicotinamide.
C.
NAD + also plays an important role in cholera infections. Cholera toxin has an enzymatic activity that transfers ADP-ribose from NAD + to a G protein involved in regulating ion fluxes in the cells lining the gut. This ADP-ribosylation blocks water retention, causing the diarrhea and dehydration characteristic of cholera.
D.
Both nicotinic acid and nicotinamide cure pellagra.