Nucleotide Inhibition of Glyoxalase II

Nucleotide Inhibition of Glyoxalase II

Date: May 1999
Creator: Gillis, Glen S
Description: The glyoxalase system mediates the conversion of methylglyoxal, a toxic ketoaldehyde, to D-lactic acid. The system is composed of two enzymes, glyoxalase I (Glo-I) and glyoxalase II (Glo-II), and exhibits an absolute requirement for a catalytic quantity of glutathione (GSH). Glo-I catalyzes the isomerization of a hemithioacetal, formed non-enzymatically from methylglyoxal and GSH, to the corresponding a -D-hydroxyacid thioester, s-D-lactoylglutathione (SLG). Glo-II catalyzes the irreversible breakdown of SLG to D-lactate and GSH. We have observed that ATP or GTP significantly inhibits the Glo-II activity of tissue homogenates from various sources. We have developed a rapid, one step chromatography procedure to purify Glo-II such that the purified enzyme remains "sensitive" to inhibition by ATP or GTP (Glo-II-s). Studies indicate that inhibition of Glo-II-s by nucleotides is restricted to ATP, GTP, ADP, and GDP, with ATP appearing most effective. Kinetics studies have shown that ATP acts as a partial non-competitive inhibitor of Glo-II-s activity, and further suggest that two kinetically distinguishable forms of the enzyme exist. The sensitivity of pure Glo-II-s to nucleotide inhibition is slowly lost on storage even at -80° C. This loss is accelerated at higher temperatures or in the presence of ATP. Kinetics studies on the resultant "insensitive" ...
Contributing Partner: UNT Libraries
Scientific Considerations of Olestra as a Fat Substitute

Scientific Considerations of Olestra as a Fat Substitute

Date: December 1999
Creator: Rattagool, Kullakan
Description: Olestra is, a sucrose polyester, a noncaloric fat substitute, made from sucrose and several fatty acid esters. It has been approved by the FDA as a food additive used in preparing low-fat deep-frying foods such as savory snacks. Available literature on olestra was evaluated that had both positive and negative connotations. Clinical trials in numerous species of animals including humans were conducted to determine if olestra would affect the utilization and absorption of macro- and micronutrients; the effects of olestra on growth, reproduction, or its toxicity were also examined. The roles of olestra as a fat substitute, how it could effect on humans and the environment, and the potential impacts from its use in large amounts were assessed. Olestra can be removed from the environment by aerobic bacteria and fungi which may be isolated from activated sludge and soils.
Contributing Partner: UNT Libraries