title: Differential response of orthologous L,L-diaminopimelate aminotransferases (DapL) to enzyme inhibitory antibiotic lead compounds.
abstract: L,L-Diaminopimelate aminotransferase (DapL) is an enzyme required for the biosynthesis of meso-diaminopimelate (m-DAP) and L-lysine (Lys) in some bacteria and photosynthetic organisms. m-DAP and Lys are both involved in the synthesis of peptidoglycan (PG) and protein synthesis. DapL is found in specific eubacterial and archaeal lineages, in particular in several groups of pathogenic bacteria such as Leptospira interrogans (LiDapL), the soil/water bacterium Verrucomicrobium spinosum (VsDapL) and the alga Chlamydomonas reinhardtii (CrDapL). Here we present the first comprehensive inhibition study comparing the kinetic activity of DapL orthologs using previously active small molecule inhibitors formerly identified in a screen with the DapL of Arabidopsis thaliana (AtDapL), a flowering plant. Each inhibitor is derived from one of four classes with different central structural moieties: a hydrazide, a rhodanine, a barbiturate, or a thiobarbituate functionality. The results show that all five compounds tested were effective at inhibiting the DapL orthologs. LiDapL and AtDapL showed similar patterns of inhibition across the inhibitor series, whereas the VsDapL and CrDapL inhibition patterns were different from that of LiDapL and AtDapL. CrDapL was found to be insensitive to the hydrazide (IC₅₀ >200 μM). VsDapL was found to be the most sensitive to the barbiturate and thiobarbiturate containing inhibitors (IC₅₀ ∼5 μM). Taken together, the data shows that the homologs have differing sensitivities to the inhibitors with IC₅₀ values ranging from 4.7 to 250 μM. In an attempt to understand the basis for these differences the four enzymes were modeled based on the known structure of AtDapL. Overall, it was found that the enzyme active sites were conserved, although the second shell of residues close to the active site were not. We conclude from this that the altered binding patterns seen in the inhibition studies may be a consequence of the inhibitors forming additional interactions with residues proximal to the active site, or that the inhibitors may not act by binding to the active site. Compounds that are specific for DapL could be potential biocides (antibiotic, herbicide or algaecide) that are nontoxic to animals since animals do not contain the enzymes necessary for PG or Lys synthesis. This study provides important information to expand our current understanding of the structure/activity relationship of DapL and putative inhibitors that are potentially useful for the design and or discovery of novel biocides.
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
authors.forename: Shaun M K
authors.initials: SM
authors.lastname: McKinnie
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Rodriguez-Lopez
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
authors.forename: John C
authors.initials: JC
authors.lastname: Vederas
authors.affiliation: Biomolecular Interaction Centre, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Crowther
authors.affiliation: Biomolecular Interaction Centre, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
authors.forename: Hironori
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Biomolecular Interaction Centre, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand; Department of Biochemistry and Molecular Biology, Bio21 Molecular and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia.
authors.forename: Renwick C J
authors.initials: RC
authors.lastname: Dobson
authors.affiliation: Department of Plant Biology and Pathology, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Leustek
authors.affiliation: The Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623-5603, USA.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Triassi
authors.affiliation: The Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623-5603, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Wheatley
authors.affiliation: The Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623-5603, USA. Electronic address: aohsbi@rit.edu.
authors.forename: André O
authors.initials: AO
authors.lastname: Hudson
mesh_terms: D000595:Amino Acid Sequence; D003960:Diaminopimelic Acid / Q000737:chemistry* / Q000378:metabolism; D007854:Lead / Q000494:pharmacology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010457:Peptidoglycan; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D000637:Transaminases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D010457:Peptidoglycan; D007854:Lead; D003960:Diaminopimelic Acid; D000637:Transaminases
keywords: Algaecide; Antibiotics; Diaminopimelate; Herbicide; Peptidoglycan; l,l-Diaminopimelate aminotransferase; l-Lysine