Evaluation of the risk of foreign compounds depends upon understanding the mechanism of their degradation. Hydrolytic enzymes, such as epoxide hydrolases or esterases and amidases, protect us against many environmental chemicals, and some of them also have biological functions. Our main objective is to understand the role of these hydrolase enzymes on human health, from both natural and exogenous influences. By studying them we can identify new targets for the action of drugs and nutraceuticals to improve health. This knowledge will also predict risk from environmental chemicals that increase or decrease the levels of hydrolytic enzymes.
To study these enzymes, we have cloned the epoxide hydrolases from rodent and human. We cloned 15 esterases and amidases from human. We developed fluorescence-based assays for most of these enzymes. We are using medicinal chemistry approaches associated with pharmacokinetic studies to synthesize transition state inhibitors that are potent and active in vivo. We already developed inhibitors for the soluble epoxide hydrolase (sEH), the microsomal epoxide hydrolase (mEH), carboxyl-esterases (CEs), fatty acid amide hydrolase (FAAH), and 2-acyl glycerol lipase (2-AGL).
Immunoassay/Biosensor. Assessment of human and environmental exposure to environmental chemicals demands a variety of studies that require the analysis of hundreds or thousands of samples that differ widely in their composition. These samples may need extensive cleanup in order to measure the pesticides without interference. Methods such as these can be very expensive and time-consuming. Immunoassay, based on the detection of pesticides by antibodies, is one answer to the need for rapid, economical analysis. Immunoassays are sensitive enough to detect the low levels of pesticides found in water, are rapid to conduct, may be conducted in the field or laboratory, and usually require less sample cleanup prior to analysis. We have developed assays for more than 40 chemicals, particularly pesticides such as pyrethroids and triazines and environmental contaminants such as dioxin, and polybrominated diphenyl ethers (PBDEs). Many have been applied/validated for analysis in soil, sediment, water, urine, serum and food. A significant portion of our work is directed to improving throughput, developing novel detection reagents such as lanthanide nanoparticle fluorophores and phage peptides and applying these to innovative biosensor formats.
There are several immunoassays that Dr. Hammock's lab has developed, and the reagents are available for distribution. A list of these assays and contact information can be found here.
Insects can have extremely detrimental effects on human welfare primarily in terms of 1) their ability to damage food/fiber crops and 2) their ability to transmit disease not only in humans but also livestock and plants used by humans. In order to reduce these detrimental effects, we are studying ways to control pest insect populations through biological targets such as the insect endocrine system and chemical approaches such as pyrethroid insecticides.
Juvenile hormone (JH) is a key lipophilic hormone that regulates metamorphosis, behavior, reproduction, and other key events in insects. A major emphasis of the laboratory’s “biological approach” for pest insect control is the study of two JH hydrolytic enzymes, JH esterase (JHE) and JH epoxide hydrolase (JHEH). These enzymes are known to intricately regulate JH titers through metabolism but may also function as synthetic enzymes in terms of the production of JH acid, JH diol, and/or JH acid-diol (Fig. 1).
The use of synthetic chemical insecticides such as pyrethroids is a key strategy for the control of agriculture pests and disease vectors. A major problem with the use and misuse of chemical insecticides is the development of resistance. Target site insensitivity and enhanced detoxification are two of the major mechanisms through which insects can become insecticide resistant. Insecticide detoxification enzymes include esterases, GSTs, and cytochrome P450s. Our laboratory is involved in the identification and characterization of these insecticide detoxification enzymes and the genes that encode these proteins. By identifying and characterizing these detoxification proteins, we hope to get a better understanding of the molecular mechanisms of insecticide resistance. From a practical point of view, these proteins can be used as targets for the development of quantitative and high throughput assays for the detection of insecticide resistance.