Cytochrome P450 Research

Cytochrome P450 Enzymes; CYPs

My basic research program focuses on the cytochrome P450 superfamily of proteins with an emphasis on their evolution and function in aquatic species such as fish.  Cytochrome P450 enzymes, or CYPs, are heme proteins critical for generation of major biological signaling molecules (e.g. steroid hormones) and for the detoxification of xenobiotics (e.g. drugs, environmental contaminants).  CYPs are a key component of the defensome – the genes that aid in protection and defense from toxic compounds.  Vertebrate species have 50-100 CYP genes in their genome but the function of many of these genes in non-mammalian species is unclear.  We have a primary interest in understanding the evolution and function of CYPs in aquatic organisms.

CYP4 phylogeny

Our projects involve genome annotation of CYP sequences, phylogenetic studies of CYP families, protein expression and functional testing of CYPs.  This research raises fundamental questions about CYP protein function and attracts students with strong interests in protein evolution, bioinformatics, molecular biology and biochemistry.

Bioinformatics approaches are used in genome annotations of CYP genes and phylogenetic studies that raise functional hypotheses regarding novel CYP sequences.  With each new genome completed, an array of CYP sequences are identified for which functional knowledge is lacking.  Our basic science research is directly aimed at uncovering the function of these novel genes and understanding the capacity of CYP systems in aquatic species.

Spectrum of expressed zebrafish CYP

Much of the tools used to examine CYP function were designed for mammalian systems.  My lab has undertaken experiments meant to directly compare and contrast the function of CYP systems in mammalian and piscine liver; the major organ for xenobiotic metabolism.  We have tested the capacity of fish hepatic CYP mediated metabolism using fluorogenic substrates and examined CYP enzyme inhibition with typical mammalian CYP inhibitors.  Since the liver expresses multiple CYP isoforms, we have expressed several CYP enzymes including those in the CYP1 and CYP3 family to investigate the function of specific CYPs important for drug, xenobiotic, and estradiol metabolism.

NAPH and NADP+ detected by CE

Our ability to study CYP systems is limited by the available tools.  In collaboration with the lab of Dr. Philip Britz-McKibbin (Department of Chemistry, McMaster University), we have developed a capillary electrophoresis assay for CYP function.  CYPs require the donation of electrons from NADPH to complete their catalytic cycle, typically hydroxylation reactions.  While most assays monitor the loss of substrate or generation of metabolite, these assays are very specific for single compounds.  The measurement of NADPH consumption would provide a generic assay for CYP activity that would allow for screening of CYP function with low cost and higher throughput.  Our current research is aimed at using high throughput screening approaches to build structure-activity relationships and uncover function of our expressed CYP proteins.  This research is completed in McMaster’s High Throughput Screening Laboratory using libraries of chemicals derived from natural products and off-label drugs.

This research has been funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery and Accelerator Programs, the Canadian Foundation of Innovation (CFI), and Ontario Innovation Trust (OIT).

Recent Posts

Women of Distinction: 2018 Edition

That special time of year is almost upon us again, the chance to celebrate Hamilton’s Women of Distinction.  And like many years, the McMaster community is out in full force.  I’m not sure exactly what it is about our community that produces so many exceptional women but in many years McMaster women make up over half of all nominees and every single Young Woman of Distinction.  That is an achievement for which the McMaster community should be very, very proud.  I encourage you to read their biographies and hear their stories to find some great inspiration.  These women are smart, enthusiastic, energetic, exceptional and contribute to our community in so many unique ways.   For me, the best categories to read about are at the opposite end of the spectrum, the Life Time Achievement nominees and the Young Woman of Distinctions.  I am really not sure how anyone in either category can achieve so much.

2018 is a special year for our lab because Ushma Purohit is a nominee in the Young Woman of Distinction category.  Ushma has been a Wilson Tox Lab member since her 2nd year of university, when she asked me to supervise her in an experiential learning course.  She was keen to get into a lab and gain some hands on experience and excited to join a new area for our lab.  Ushma worked with another stellar undergraduate researcher, Abby Lee, to develop hydra as a model system to study the impacts of human pharmaceuticals on aquatic species.  Abby was completing her senior thesis, assessing the effects of chronic exposure of hydra to an anti-epileptic and an anti-depressant pharmaceutical.  Ushma learned how to prepare, stain, and count the different cell typess from hydra so we could identify whether there were changes in the proportions of cell types after exposure.  That research is now being written into a manuscript for publication.  I often point to this area of our research program to demonstrate how impactful undergraduate researchers can be.

Ushma has continued to volunteer and complete research course work in my lab and is now in her senior year.  She has gone from assisting others on research to running her own.  Her senior thesis research focuses on the anti-microbial compound triclosan and whether this impacts compound negatively impacts hydra biology.  She is a bright and independent researcher with a great future.  Yet, this is just the tip of the iceberg.  Beyond her classes and research, Ushma has been contributing to her communities at McMaster, in the larger city of Hamilton, and beyond.

So what does it take to be a Young Woman of Distinction?  Well let’s just list two of Ushma’s accomplishments outside of the lab.  Ushma founded the first Canadian chapter of the organization She’s the First, which champions education of girls in low-income countries.  The McMaster chapter has focused on raising funds and education campaigns including conferences, art showcases, recreational events, and awareness videos, to encourage the conversation around intersectional feminisim within the McMaster community. Within Hamilton, this club has hosted educational workshops at the local Native Women’s Centre on health, self-care and other topics and in Hamilton’s elementary schools to educate students on topics such as communication and the media, body image and bullying, and female leadership. Not so surprisingly, this club has won two awards within its first year; a McMaster Student Union award for the Best New Club of the Year and an award from the parent organization for Outstanding Achievement in Community Engagement.

Ushma is the current President of the UNICEF club at McMaster University, a club she has been active in for over 3 years.  It is one of the largest clubs on campus and raises funds to support the health and education of children and raise awareness of humanitarian issues within the McMaster community.  The McMaster UNICEF club sends over 100 volunteers to the Children’s International Learning Centre and supports education of young children through a variety of initiatives.

What has Ushma’s nomination meant to her?

“The experience of becoming a nominee for the Women of Distinction awards has been a lot more meaningful for me than I could have imagined. This nomination provided me with the opportunity to learn about and interact with some of the most driven, hard-working and talented women in Hamilton. As an individual who is currently at the advent of her career, experiences like this play a pivotal role in moulding my ambitions and aspirations for the future. Regardless of who wins the Young Woman of Distinction Award, I believe that as nominees, we have won an eye-opening experience that we will carry with us in the years to come.”

Feel inspired yet?  This isn’t a complete list of all she does, but just a couple of highlights of what this young woman of distinction has already accomplished.  Ushma is just one of 34 nominees for the 2018 YWCA Hamilton Women of Distinction awards.  Take a few minutes and read about who they are and what they do.  Regardless of who wins the awards, McMaster and Hamilton are the big winners here because these women are exceptional.

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