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1.  Potent Inhibition of the C-P Lyase Nucleosidase PhnI by ImmucillinA-Triphosphate 
Biochemistry  2013;52(42):10.1021/bi4013287.
The C-P lyase complex in bacteria catalyzes the transformation of phosphonates to orthophosphate under conditions of phosphate starvation. The first committed step in the C-P lyase catalyzed reaction is the displacement of adenine from MgATP by phosphonate substrates to yield ribose-1-phosphonate-5-triphosphate (RPnTP). In the C-P lyase complex this reaction is catalyzed by the nucleosidase PhnI, and modulated by the addition of PhnG, PhnH and PhnL. Here we describe the synthesis of Immucillin-A triphosphate, a mimic of the transition state structure for the nucleosidase reaction catalyzed by PhnI. This compound inhibits PhnI with a dissociation constant of 20 nM at pH 7.5.
PMCID: PMC3838859  PMID: 24111876
2.  Impact of natalizumab on patient-reported outcomes in multiple sclerosis: a longitudinal study 
Natalizumab (Tysabri, Biogen Idec and Elan Pharmaceuticals) significantly reduces the relapse rate and disability progression, and improves health-related quality of life (HRQoL), in patients with relapsing-remitting multiple sclerosis. We investigated the impact of natalizumab on patient-reported outcomes (PROs) in a real-world setting.
PRO data were collected from patients enrolled in a longitudinal real-world study using validated measures administered as surveys before the patients initiated natalizumab treatment and after the 3rd, 6th, and 12th monthly infusion. HRQoL, ability to carry out daily activities, disability level, and impact on cognitive functioning and fatigue were assessed.
A total of 333 patients completed 12 months of assessments. After 12 months of natalizumab treatment, 69% to 88% of patients reported a positive outcome (either an improvement or no further decline) in all PRO measures assessed. Significant improvements in general and disease-specific HRQoL were observed after three infusions, both with physical (p < .01) and psychological (p < .001) measures, and were sustained after 12 infusions (all p < .001). The impact of multiple sclerosis on cognitive functioning and fatigue was significantly reduced (both p < .001 after 3 and 12 infusions).
PRO measures were improved with natalizumab in a real-world setting. The improvements were observed as early as after 3 months and sustained over a 12-month period. The improvements in PROs show that, in clinical practice, the clinical benefits of natalizumab are translated into patient-reported benefits.
PMCID: PMC3543243  PMID: 23270428
Cognitive function; Health-related quality of life; Multiple sclerosis; Natalizumab; Patient-reported outcomes
3.  Intermediates in the Transformation of Phosphonates to Phosphate by Bacteria 
Nature  2011;480(7378):570-573.
PMCID: PMC3245791  PMID: 22089136
4.  Catalytic Mechanism and Three-Dimensional Structure of Adenine Deaminase† 
Biochemistry  2011;50(11):1917-1927.
Adenine deaminase (ADE) catalyzes the conversion of adenine to hypoxanthine and ammonia. The enzyme isolated from Escherichia coli using standard expression conditions was low for the deamination of adenine (kcat = 2.0 s−1; kcat/Km = 2.5 × 103 M−1 s−1). However, when iron was sequestered with a metal chelator and the growth medium was supplemented with Mn2+ prior to induction, the purified enzyme was substantially more active for the deamination of adenine with values of kcat and kcat/Km of 200 s−1 and 5 × 105 M−1s−1, respectively. The apo-enzyme was prepared and reconstituted with Fe2+, Zn2+, or Mn2+. In each case, two enzyme-equivalents of metal were necessary for reconstitution of the deaminase activity. This work provides the first example of any member within the deaminase sub-family of the amidohydrolase superfamily (AHS) to utilize a binuclear metal center for the catalysis of a deamination reaction. [FeII/FeII]-ADE was oxidized to [FeIII/FeIII]-ADE with ferricyanide with inactivation of the deaminase activity. Reducing [FeIII/FeIII]-ADE with dithionite restored the deaminase activity and thus the di-ferrous form of the enzyme is essential for catalytic activity. No evidence for spin-coupling between metal ions was evident by EPR or Mössbauer spectroscopies. The three-dimensional structure of adenine deaminase from Agrobacterium tumefaciens (Atu4426) was determined by X-ray crystallography at 2.2 Å resolution and adenine was modeled into the active site based on homology to other members of the amidohydrolase superfamily. Based on the model of the adenine-ADE complex and subsequent mutagenesis experiments, the roles for each of the highly conserved residues were proposed. Solvent isotope effects, pH rate profiles and solvent viscosity were utilized to propose a chemical reaction mechanism and the identity of the rate limiting steps.
PMCID: PMC3059353  PMID: 21247091
5.  Enzymatic Deamination of the Epigenetic Base N-6-Methyladenine 
Two enzymes of unknown function from the amidohydrolase superfamily were discovered to catalyze the deamination of N-6-methyladenine to hypoxanthine and methyl amine. The methylation of adenine in bacterial DNA is a common modification for the protection of host DNA against restriction endonucleases. The enzyme from Bacillus halodurans, Bh0637, catalyzes the deamination of N-6-methyladenine with a kcat of 185 s−1 and a kcat/Km of 2.5 × 106 M−1 s−1. Bh0637 catalyzes the deamination of N-6-methyladenine two orders of magnitude faster than adenine. A comparative model of Bh0637 was computed using the three-dimensional structure of Atu4426 (PDB code: 3NQB) as a structural template and computational docking was used to rationalize the preferential utilization of N-6-methyladenine over adenine. This is the first identification of an N-6-methyladenine deaminase (6-MAD).
PMCID: PMC3043370  PMID: 21275375
6.  Metabolic Screening After the American Diabetes Association's Consensus Statement on Antipsychotic Drugs and Diabetes 
Diabetes Care  2009;32(6):1037-1042.
Several second-generation antipsychotic (SGA) drugs have been associated with weight gain, hyperglycemia, and dyslipidemia. We evaluated whether glucose and lipid testing increased after the American Diabetes Association (ADA) consensus statement recommending metabolic monitoring for SGA-treated patients.
Laboratory claims for serum glucose and lipid testing were identified for an incident cohort of 18,876 adults initiating SGA drugs in a U.S. commercial health plan (2001–2006) and a control group of 56,522 adults with diabetes not receiving antipsychotics. Interrupted time-series models were used to estimate the effect of ADA recommendations on baseline and annual testing trends after adjusting for differences in age, sex, mental health diagnoses, and cardiovascular risk using propensity score matching.
Mean baseline testing rates for SGA-treated patients during the study period were 23% (glucose) and 8% (lipids). Among persistent users of SGA medication, annual testing rates were 38% (glucose) and 23% (lipid). Before the ADA statement, screening rates for SGA-treated patients were increasing (glucose: baseline 3.6% per year, annual 7.2% per year; lipid: baseline 1.2% per year, annual 4.8% per year; P < 0.001 for each trend). Increases were similar to background testing trends in control subjects. The ADA statement was not associated with an increase in screening rates.
In a commercially insured population, glucose and lipid testing for SGA-treated adults was infrequent. A gradual increase in screening rates occurred over the 6-year period, but the changes were not temporally associated with the ADA statement. More effort is needed to improve diabetes and dyslipidemia screening in these at-risk patients.
PMCID: PMC2681020  PMID: 19244091

Results 1-6 (6)