(16) The effects of indole-3-acetic acid on human and horse serum butyrylcholinesterase

Butyrylcholinesterase (BChE) constitutes the first line defense in the serum of higher organisms and is a marker for toxic exposure. Indole-3-acetic acid (IAA) is a major plant growth hormone of the auxin class, affecting cell enlargement, and differentiation. As a result of the industrial usage, this agrochemical is consumed by non-target organisms. In this study, the interaction of IAA with purified human and horse serum BChEs were investigated. Both BChE species displayed biphasic hill plots using butyrylthiocholine as substrate. IAA interaction with BChE species was stable and concentration dependent. IAA was found to be linear-mixed type inhibitor for human serum BChE, and alpha and the Ki values were 2.15 +/- 1.09 mM and 3.09 +/- 0.95 mM, respectively. With horse enzyme IAA displayed uncompetitive inhibition with the Ki value of 1.05 +/- 0.09 mM. Acquisition of large amounts of IAA is unlikely but it can be taken as a basis for future inhibitor designs.