362 research outputs found

    Kinetic and Structural Analysis of Substrate Specificity in Two Copper Amine Oxidases from Hansenula polymorpha

    Get PDF
    The structural underpinnings of enzyme substrate specificity are investigated in a pair of copper amine oxidases (CAOs) from Hansenula polymorpha (HPAO-1 and HPAO-2). The X-ray crystal structure (to 2.0 Å resolution) and steady state kinetic data of the second copper amine oxidase (HPAO-2) are presented for comparison to HPAO-1. Despite 34 % sequence identity and superimposable active site residues implicated in catalysis, the enzymes vary considerably in their substrate entry channel. The previously studied CAO, HPAO-1, has a narrow substrate channel. In contrast HPAO-2 has a wide funnel-shaped substrate channel, which also contains a side-chamber. In addition, there are a number of amino acid changes within the channels of HPAO-2 and HPAO-1 that may sterically impact the ability of substrates to form covalent Schiff base catalytic intermediates and to initiate chemistry. These differences can partially explain the greatly different substrate specificities as characterized by kcat/Km value differences: in HPAO-1, the kcat/Km for methylamine is 330-fold greater than for benzylamine, whereas in HPAO-2 it is benzylamine that is the better substrate by 750-fold. In HPAO-2 an inflated Dkcat/Km(methylamine) in relation to Dkcat/Km(benzylamine) indicates that proton abstraction has been impeded more than substrate release. In HPAO-1, Dkcat/Km(S) changes little with the slow substrate, and indicates a similar increase in the energy barriers that control both substrate binding and subsequent catalysis. In neither case is kcat/Km for the second substrate, O2, significantly altered. These results reinforce the modular nature of the active sites of CAOs and show that multiple factors contribute to substrate specificity and catalytic efficiency. In HPAO-1, the enzyme with the smaller substrate binding pocket, both initial substrate binding and proton loss are affected by an increase in substrate size, while in HPAO-2, the enzyme with the larger substrate binding pocket, the rate of proton loss is differentially affected when a phenyl substituent in substrate is reduced to the size of a methyl group

    The Effect of Race, Sex, and Insurance Status on Time-to-Listing Decisions for Liver Transplantation

    Get PDF
    Fair allocation of organs to candidates listed for transplantation is fundamental to organ-donation policies. Processes leading to listing decisions are neither regulated nor understood. We explored whether patient characteristics affected timeliness of listing using population-based data on 144,507 adults hospitalized with liver-related disease in Pennsylvania. We linked hospitalizations to other secondary data and found 3,071 listed for transplants, 1,537 received transplants, and 57,020 died. Among candidates, 61% (n = 1,879) and 85.5% (n = 2,626) were listed within 1 and 3 years of diagnosis; 26.7% (n = 1,130) and 95% (n = 1,468) of recipients were transplanted within 1 and 3 years of listing. Using competing-risks models, we found few overall differences by sex, but both black patients and those insured by Medicare and Medicaid (combined) waited longer before being listed. Patients with combined Medicare and Medicaid insurance, as well as those with Medicaid alone, were also more likely to die without ever being listed. Once listed, the time to transplant was slightly longer for women, but it did not differ by race/ethnicity or insurance. The early time period from diagnosis to listing for liver transplantation reveals unwanted variation related to demographics that jeopardizes overall fairness of organ allocation and needs to be further explored

    Pharmacogenomic Variants May Influence the Urinary Excretion of Novel Kidney Injury Biomarkers in Patients Receiving Cisplatin

    Get PDF
    Nephrotoxicity is a dose limiting side effect associated with the use of cisplatin in the treatment of solid tumors. The degree of nephrotoxicity is dictated by the selective accumulation of cisplatin in renal tubule cells due to: (1) uptake by organic cation transporter 2 (OCT2) and copper transporter 1 (CTR1); (2) metabolism by glutathione S-transferases (GSTs) and γ-glutamyltransferase 1 (GGT1); and (3) efflux by multidrug resistance-associated protein 2 (MRP2) and multidrug and toxin extrusion protein 1 (MATE1). The purpose of this study was to determine the significance of single nucleotide polymorphisms that regulate the expression and function of transporters and metabolism genes implicated in development of acute kidney injury (AKI) in cisplatin treated patients. Changes in the kidney function were assessed using novel urinary protein biomarkers and traditional markers. Genotyping was conducted by the QuantStudio 12K Flex Real-Time PCR System using a custom open array chip with metabolism, transport, and transcription factor polymorphisms of interest to cisplatin disposition and toxicity. Traditional and novel biomarker assays for kidney toxicity were assessed for differences according to genotype by ANOVA. Allele and genotype frequencies were determined based on Caucasian population frequencies. The polymorphisms rs596881 (SLC22A2/OCT2), and rs12686377 and rs7851395 (SLC31A1/CTR1) were associated with renoprotection and maintenance of estimated glomerular filtration rate (eGFR). Polymorphisms in SLC22A2/OCT2, SLC31A1/CTRI, SLC47A1/MATE1, ABCC2/MRP2, and GSTP1 were significantly associated with increases in the urinary excretion of novel AKI biomarkers: KIM-1, TFF3, MCP1, NGAL, clusterin, cystatin C, and calbindin. Knowledge concerning which genotypes in drug transporters are associated with cisplatin-induced nephrotoxicity may help to identify at-risk patients and initiate strategies, such as using lower or fractionated cisplatin doses or avoiding cisplatin altogether, in order to prevent AKI

    The contribution of smoking-attributable mortality to differences in mortality and life expectancy among US African-American and white adults, 2000-2019

    Get PDF
    Background: The role of smoking in racial disparities in mortality and life expectancy in the United States has been examined previously, but up-to-date estimates are generally unavailable, even though smoking prevalence has declined in recent decades. Objective: We estimate the contribution of smoking-attributable mortality to observed differences in mortality and life expectancy for US African-American and white adults from 2000-2019. Methods: The indirect Preston-Glei-Wilmoth method was used with national vital statistics and population data and nationally representative never-smoker lung cancer death rates to estimate the smoking-attributable fraction (SAF) of deaths in the United States by sex-race group from 2000-2019. Mortality rates without smoking-attributable mortality were used to estimate life expectancy at age 50 (e_50) by group during the period. Results: African-American men had the highest estimated SAF during the period, beginning at 26.4Š (95Š CI:25.0Š-27.8Š) in 2000 and ending at 12.1Š (95Š CI:11.4Š-12.8Š) in 2019. The proportion of the difference in e_50 for white and African-American men that was due to smoking decreased from 27.7Š to 14.8Š. For African-American and white women, the estimated differences in e_50 without smoking-attributable mortality were similar to observed differences. Conclusions: Smoking continues to contribute to racial disparities in mortality and life expectancy among men in the United States. Contribution: We present updated estimates of the contribution of smoking to mortality differences in the United States using nationally representative data sources

    A Novel BMPR2 Mutation Associated with Pulmonary Arterial Hypertension in an Octogenarian

    Get PDF
    We describe the case of an 83-year-old man with a family history of pulmonary hypertension (PH) who presented with severe pulmonary arterial hypertension (PAH) and later tested positive for a novel bone morphogenetic protein receptor 2 (BMPR2) gene mutation. To our knowledge, this may be the oldest reported patient with PAH in whom a BMPR2 mutation was initially identified

    Characterization of a new full length TMPRSS3 isoform and identification of mutant alleles responsible for nonsyndromic recessive deafness in Newfoundland and Pakistan

    Get PDF
    BACKGROUND: Mutant alleles of TMPRSS3 are associated with nonsyndromic recessive deafness (DFNB8/B10). TMPRSS3 encodes a predicted secreted serine protease, although the deduced amino acid sequence has no signal peptide. In this study, we searched for mutant alleles of TMPRSS3 in families from Pakistan and Newfoundland with recessive deafness co-segregating with DFNB8/B10 linked haplotypes and also more thoroughly characterized the genomic structure of TMPRSS3. METHODS: We enrolled families segregating recessive hearing loss from Pakistan and Newfoundland. Microsatellite markers flanking the TMPRSS3 locus were used for linkage analysis. DNA samples from participating individuals were sequenced for TMPRSS3. The structure of TMPRSS3 was characterized bioinformatically and experimentally by sequencing novel cDNA clones of TMPRSS3. RESULTS: We identified mutations in TMPRSS3 in four Pakistani families with recessive, nonsyndromic congenital deafness. We also identified two recessive mutations, one of which is novel, of TMPRSS3 segregating in a six-generation extended family from Newfoundland. The spectrum of TMPRSS3 mutations is reviewed in the context of a genotype-phenotype correlation. Our study also revealed a longer isoform of TMPRSS3 with a hitherto unidentified exon encoding a signal peptide, which is expressed in several tissues. CONCLUSION: Mutations of TMPRSS3 contribute to hearing loss in many communities worldwide and account for 1.8% (8 of 449) of Pakistani families segregating congenital deafness as an autosomal recessive trait. The newly identified TMPRSS3 isoform e will be helpful in the functional characterization of the full length protein

    Measurement Bias in Caregiver-Report of Early Childhood Behavior Problems across Demographic Factors in an Echo-Wide Diverse Sample

    Get PDF
    BACKGROUND: Research and clinical practice rely heavily on caregiver-report measures, such as the Child Behavior Checklist 1.5-5 (CBCL/1.5-5), to gather information about early childhood behavior problems and to screen for child psychopathology. While studies have shown that demographic variables influence caregiver ratings of behavior problems, the extent to which the CBCL/1.5-5 functions equivalently at the item level across diverse samples is unknown. METHODS: Item-level data of CBCL/1.5-5 from a large sample of young children ( RESULTS: Items with the most impactful DIF across child and caregiver groupings were identified for Internalizing, Externalizing, and total Problems. The robust item sets, excluding the high DIF items, showed good reliability and high correlation with the original Internalizing and total Problems scales, with lower reliability for Externalizing. Language version of CBCL administration, education level and sex of the caregiver respondent showed the most significant impact on MI, followed by child age. Sensitivity analyses revealed that child race has a unique impact on DIF over and above socioeconomic status. CONCLUSIONS: The CBCL/1.5-5, a caregiver-report measure of early childhood behavior problems, showed bias across demographic groups. Robust item sets with less DIF can measure Internalizing and total Problems equally as well as the full item sets, with slightly lower reliability for Externalizing, and can be crosswalked to the metric of the full item set, enabling calculation of normed T scores based on more robust item sets
    corecore