aakbThis problem may not solved just by knowing the above equation, if you're like me and get confused when you see lots of numbers and letters together.
You need to use Kcat/Km to find the catalytic efficiency for both E487 and K487. Doing this, you'll see both A and B are true. Catalytic efficiency for K487 is 9.5/5600 = 0.002, which is decreased (A) and for e487 you get 180/37 = 4, making B true. Now how do you pick between A and B? The patient has disulfram-like reactions whenever he consumes alcohol since his acetylaldehyde dehydrogenase is slower (decreased catalytic efficiency), seen w/ K487, which the patient actually has if the question is read closely. So if you knew he had k487 from reading the confusing question stem it would have been easy to pick between A and B but if you're like me and can't seem to make those connections quickly, knowing something about ethanol metabolism helps. +2
tekkenman101The fastest way to answer this question is realizing the patient has the oriental variant, so all options regarding E can be excluded. Then you can see that the Km of the K-variant is much larger than the E-one.
Larger Km = decreased binding = decreased turnover/catalytic efficiency.
30 seconds tops.+8
chj7Not wanting people to get confused here. Km does reflect binding (higher Km means you need more substrate to reach same Vmax--> decreased binding). However, turnover number (the number of times each enzyme site converts substrate to product per unit time) is reflected by Kcat, NOT Km. One way to determine catalytic efficiency is Kcat/Km, which is also termed the specificity constant. You CANNOT answer this question by only looking at Km.+4
submitted by โacerj(13)
Catalytic efficiency is defined as K_cat/K_M.
If you know what that is (I did not), then this problem is a simple division.
See here for more info (stop at the first line of the article for your own sanity): https://en.wikipedia.org/wiki/Specificity_constant