Enzyme Inhibition and Regulation (5E) Practice Test

Researchers screened two small molecules (A and B) against acetylcholinesterase (AChE) using acetylcholine as substrate. Control parameters: $K_m$ = 0.05 mM, $V_{max}$ = 200 \u03bcmol\u00b7min$^{-1}$\u00b7mg$^{-1}$. With inhibitor A, $K_m$ increased to 0.20 mM and $V_{max}$ remained 200. With inhibitor B, $K_m$ remained 0.05 mM and $V_{max}$ decreased to 100. Based on the experiment, which conclusion about enzyme inhibition is most consistent with the data?

A mitochondrial dehydrogenase in the TCA cycle was studied in vitro. Control kinetics for substrate S were $K_m$ = 0.10 mM and $V_{max}$ = 60 \u03bcmol\u00b7min$^{-1}$\u00b7mg$^{-1}$. With 10 \u03bcM Inhibitor Y present, the measured $K_m$ remained 0.10 mM but $V_{max}$ decreased to 30 \u03bcmol\u00b7min$^{-1}$\u00b7mg$^{-1}$. Which statement best describes the effect of Inhibitor Y on enzyme activity?