Drew University Library : University Archives : Theses and Dissertations
    
author Joel Asabi Moses
title Investigating the Effects of pH and Salt Concentration on Substrate Inhibition of Yeast Aldo-Keto Reductase 163
abstract Aldo-keto reductases (AKRs) are a broad superfamily of NADPH-dependent oxidoreductases capable of catalyzing the reduction of many carbonyl compounds into alcohols in living systems and industrial settings. Most studied AKRs exhibit substrate saturation where they experience typical Michaelis-Menten kinetics with their substrates. However, a novel AKR isolated from ancient amber called AKR 163 experiences a phenomenon called substrate inhibition in the presence of electron withdrawing substrates such as ethyl 4-chloroacetoacetate (E4ClAA). This characteristic is often undesirable biologically and industrially since it leads to poor product yields. Unfortunately, there are few studies that aim to alleviate substrate inhibition despite its disadvantages. For these reasons, researchers used AKR 163 as a model enzyme to test the effects of pH on substrate inhibition. They found that decreasing pH reduced substrate inhibition. However, these studies used two types of buffers to gather data from a wide range of pHs, which could have led to inconsistent results. Similarly, researchers have also tested the effects of exogenous salt ions on substrate inhibition and found that adding salt decreases inhibition. Given the successes and shortcomings of these researchers, I combined these ideas to observe and explain the effects of salt ions and pH changes together on substrate inhibition using an ACES buffer system and E4ClAA as the substrate. My results confirm that lowering pH and adding salt decrease substrate inhibition individually. Furthermore, the lowest pH trial (pH 6) with 1M NaCl showed almost no signs of inhibition with up to 6 mM of substrate, and the plot resembled a Michaelis-Menten curve. These results indicate that substrate inhibition can be almost completely inhibited under those conditions.
school The College of Liberal Arts, Drew University
degree B.S. (2024)
advisor Adam Cassano
full textJMoses.pdf