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Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Speaker Abstracts
39
Elucidating the Differences between Eukaryotic and Prokaryotic Type II Pantothenate
Kinases
Lizbe Koekemoer
, Erick Strauss.
University of Stellenbosch, Stellenbosch, South Africa.
Coenzyme A (CoA) is a ubiquitous cofactor essential to all living organisms for its role in
numerous metabolic processes including energy metabolism and fatty acid biosynthesis. CoA is
biosynthesized de novo from pantothenic acid (Vitamin B5) in 5 enzymatic steps. Although these
steps are largely conserved amongst different organisms, the enzymes are not and slight
variations are found amongst the enzymes that catalyses the same step in different organsims.
These differences are what we are exploiting in the development of selective inhibitors that
targets CoA biosynthesis in pathogenic organisms, but do not affect the production thereof in
humans.
This project focuses on the first enzyme in the CoA biosynthesis pathway, panthothenate kinase
(PanK), that catalysis the ATP dependant phosphorylation of pantothenic acid to 4’-
phosphopantothenic acid. PanKs are unique in that there are three distinct PanK types (type I, II
and III) which differ in all aspects from molecular level to 3D structure. The type II PanKs are
the eukaryotic version of this enzyme, although versions thereof are also found in the pathogen
responsible for nosocomial infections, Staphylococcus aureus, and in selected Bacilli. Although
grouped together into the same type, the kinetic profiles we obtained for the prokaryotic PanKs
differ greatly from the kinetic profiles obtained with the human PanKs and also from each other.
These differences between the eukaryotic and prokaryotic enzymes can be explained from
available structural data, but this was a surprising result for the prokaryotic PanKs. In this study
we set out to explain the structural basis for the observed differences between the prokaryotic
PanKs by doing mutagenesis studies, CD analysis and co-crystallization with various ligands.
From these results we gained new insight into the method of ligand binding and the required
enzyme conformation for activity.