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This corrects the article DOI: 10.1103/PhysRevLett.119.175702.
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Nanosecond in situ x-ray diffraction and simultaneous velocimetry measurements were used to determine the crystal structure and pressure, respectively, of ramp-compressed aluminum at stress states between 111 and 475 GPa. The solid-solid Al phase transformations, fcc-hcp and hcp-bcc, are observed at 216±9 and 321±12 GPa, respectively, with the bcc phase persisting to 475 GPa. The high-pressure crystallographic texture of the hcp and bcc phases suggests close-packed or nearly close-packed lattice planes remain parallel through both transformations.
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INTRODUCTION: Adenotonsillectomy is successful at eliminating airway obstruction in the majority of otherwise normal children with obstructive sleep apnoea syndrome. Children with this condition are at significantly higher risk of post-operative respiratory complications. Identifying children at risk of post-operative respiratory complications after adenotonsillectomy for obstructive sleep apnoea syndrome remains a challenge for clinicians, especially those at district general hospitals. AIM: To review the evidence and to proffer a pragmatic approach to diagnosis and management, by classifying those at risk of post-operative respiratory complications into different risk subsets, with guidelines for management. CONCLUSION: Patients in the high risk group should be operated upon at paediatric specialist centres with intensive care facilities. Those in the moderate risk group may undergo adenotonsillectomy at their district general hospital, provided facilities for administering continuous positive airway pressure are available on-site. Most children with obstructive sleep apnoea syndrome may be classified as low risk candidates and may safely be operated upon at their local district general hospital.
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Adenoidectomia/efeitos adversos , Complicações Pós-Operatórias/epidemiologia , Transtornos Respiratórios/epidemiologia , Apneia Obstrutiva do Sono/cirurgia , Tonsilectomia/efeitos adversos , Criança , Pré-Escolar , Pressão Positiva Contínua nas Vias Aéreas , Hospitais de Distrito , Hospitais Gerais , Humanos , Lactente , Morbidade , Polissonografia , Complicações Pós-Operatórias/prevenção & controle , Transtornos Respiratórios/prevenção & controle , Fatores de Risco , Resultado do Tratamento , Reino Unido/epidemiologiaRESUMO
KHEYLRF-NH(2) (AF2) is a FMRFamide-related peptide (FaRP) present in parasitic and free-living nematodes. At concentrations as low as 10 pM, AF2 induces a biphasic tension response, consisting of a transient relaxation followed by profound excitation, in neuromuscular strips prepared from Ascaris suum. In the present study, the effects of AF2 on cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP) and inositol-1,4,5-triphosphate (IP(3)) levels were measured following muscle tension recordings from 2 cm neuromuscular strips prepared from adult A. suum. AF2 induced a concentration- and time-dependent increase in cAMP, beginning at 1 nM; cAMP levels increased by 84-fold following 1 h exposure to 1 microM AF2. cGMP and IP(3) levels were unaffected by AF2 at concentrations =1 microM. AF2-induced stimulation of cAMP was unaffected by removal of the dorsal or ventral nerve cord, even though this form of denervation abolished the excitatory phase of the tension response. The effects of 0.1 and 1 microM AF2 on cAMP were also unaffected by 10 microM SDPNFLRF-NH(2) (PF1, an inhibitory FaRP) and 10 microM PF1022A (an inhibitory cyclodepsipeptide), even though each of these peptides abolished the excitatory phase of the tension response induced by AF2. Within an alanine-scan series of AF2 analogues, only KHAYLRF-NH(2) stimulated cAMP production with equipotency to AF2; the effects of this peptide on muscle tension also mimicked AF2. Another excitatory FaRP present in nematodes, KNEFIRF-NH(2) (AF1), also stimulated cAMP production, but was 100-fold less potent than AF2. The stimulatory effects of AF1 on tension and cAMP levels were blocked by an alanine-substituted analogue of this peptide (Ala(6)-AF1, KNEFIAF-NH(2)), while the stimulatory effects of AF2 on tension and cAMP were not affected by this analogue. AF2 and AF1 increase A. suum somatic muscle cAMP by targeting different receptors. Increases in cAMP stimulated by AF2 can be decoupled from the excitatory response caused by this peptide, and it is not possible to establish a causal linkage between the contractile response elicited by this peptide and its effects on cAMP accumulation.
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Ascaris suum/metabolismo , AMP Cíclico/metabolismo , Junção Neuromuscular/metabolismo , Neuropeptídeos/farmacologia , Animais , Ascaris suum/efeitos dos fármacos , GMP Cíclico/metabolismo , Feminino , Técnicas In Vitro , Inositol 1,4,5-Trifosfato/metabolismo , Contração Muscular/efeitos dos fármacos , Junção Neuromuscular/efeitos dos fármacos , Estimulação QuímicaRESUMO
Tumour angiogenesis has recently attracted a great deal of attention as a critical part of oncogenesis and a necessary prerequisite for a malignant phenotype. Novel antiangiogenic therapy for solid tumours including laryngeal cancer is entering clinical trials. Quantifying microvessel density is considered the gold standard for measuring baseline angiogenesis and indeed 'the response to intervention'. We hypothesize that laser Doppler flux-metry could provide a non-invasive reliable method of quantifying blood flux within tumours. The aims were to determine whether a laser Doppler flux meter could be used as a reliable and reproducible method of estimating blood flux in the human larynx and to establish baseline Doppler flux recordings for the human larynx. The method used was a validation study in patients with laryngeal squamous cell cancer and normal controls. Statistical analysis was performed using SPSS software. We have demonstrated good reproducibility of laser Doppler measurements in human laryngeal mucosa (correlation coefficient 0.956 @P = 0.01). We have also derived arbitrary means of laser Doppler flux-metry in normal laryngeal mucosa and in squamous cell carcinoma of the larynx. Comparisons between normal and tumour laser Doppler flux-metry (LDF) readings showed no significant difference. We suggest that Laser Doppler flux-metry is a potentially useful tool with which to study blood flow in the larynx and propose arbitrary LDF levels for the normal and diseased human larynx.
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Carcinoma de Células Escamosas/diagnóstico por imagem , Neoplasias Laríngeas/diagnóstico por imagem , Fluxometria por Laser-Doppler/instrumentação , Desenho de Equipamento , Humanos , Estadiamento de Neoplasias , UltrassonografiaRESUMO
OBJECTIVE: To investigate and control a nosocomial outbreak of Burkholderia cepacia lower respiratory tract infection. DESIGN: Outbreak investigation and case-control study. SETTING: A 260-bed community hospital. PATIENTS: Participants were mechanically ventilated intensive care patients without cystic fibrosis. A case was defined as a hospitalized patient with a sputum culture positive for B. cepacia between January 1 and November 6, 1998. METHODS: Respiratory therapy infection control policies and practices were reviewed; laboratory and environmental studies and a retrospective case-control study were conducted. Case-patients were matched with control-patients on age, gender, diagnosis, and type of intensive care unit. RESULTS: Nine case-patients were identified; B. cepacia likely caused pneumonia in seven and colonization in two. Two respiratory therapy practices probably contributed to the transmission of B. cepacia: multidose albuterol vials were used among several patients, and nebulizer assemblies often were not dried between uses. B. cepacia was grown from cultures of three previously opened multidose vials; pulsed-field gel electrophoresis patterns of B. cepacia from seven case-patients and two multidose vials were indistinguishable. Case-patients had longer durations of heated humidified mechanical ventilation (mean, 9.8 days vs 4.4 days; P=.03) and were more likely to have exposure to one particular respiratory therapist than controls (odds ratio, undefined; 95% confidence interval, 4.7-infinity; P=.001). The association with the respiratory therapist, a temporary employee, persisted after controlling for duration of heated humidified ventilation. No new B. cepacia infections were identified after control measures were implemented. CONCLUSIONS: B. cepacia probably was transmitted among patients through use of extrinsically contaminated multidose albuterol vials. Respiratory therapy departments must pay close attention to infection control practices, particularly among new or temporary staff.
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Infecções por Burkholderia/transmissão , Burkholderia cepacia/isolamento & purificação , Infecção Hospitalar/transmissão , Contaminação de Equipamentos , Transmissão de Doença Infecciosa do Profissional para o Paciente , Nebulizadores e Vaporizadores/microbiologia , Infecções Respiratórias/transmissão , Ventiladores Mecânicos/microbiologia , Idoso , Infecções por Burkholderia/prevenção & controle , Estudos de Casos e Controles , Infecção Hospitalar/prevenção & controle , Surtos de Doenças , Eletroforese em Gel de Campo Pulsado , Feminino , Hospitais com 100 a 299 Leitos , Hospitais Comunitários , Humanos , Controle de Infecções/métodos , Controle de Infecções/normas , Unidades de Terapia Intensiva , Masculino , Pessoa de Meia-Idade , Infecções Respiratórias/prevenção & controle , Escarro/microbiologiaRESUMO
Screening has generally been successful in identifying those at risk from disease. This success has led to the belief that screening in the general population is always a good thing. However, there are pitfalls which must be avoided if screening programmes are to achieve what is intended for them.
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Programas de Rastreamento/normas , Análise Custo-Benefício , Feminino , Previsões , Humanos , Masculino , Programas de Rastreamento/economia , Programas de Rastreamento/métodos , Aceitação pelo Paciente de Cuidados de Saúde , Prevalência , Prognóstico , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Juvenile xanthogranuloma is a benign, normolipaemic, self-healing condition and a type of histiocytosis that occurs most frequently in infants and children. This condition usually presents with solitary or multiple cutaneous lesions and occasionally with visceral lesions. We report a case of juvenile xanthogranuloma occurring in the nasal cavity. We believe this is the first report, in the English literature, of juvenile xanthogranuloma occurring in this site.
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Cavidade Nasal , Doenças Nasais/diagnóstico , Xantogranuloma Juvenil/diagnóstico , Adolescente , Humanos , Masculino , Doenças Nasais/cirurgia , Xantogranuloma Juvenil/cirurgiaAssuntos
Granulomatose com Poliangiite/diagnóstico por imagem , Glândula Parótida/diagnóstico por imagem , Idoso , Diagnóstico Diferencial , Granulomatose com Poliangiite/complicações , Granulomatose com Poliangiite/cirurgia , Humanos , Masculino , Glândula Parótida/cirurgia , Sialadenite/complicações , Sialadenite/diagnóstico , Tomografia Computadorizada por Raios XRESUMO
Cellular Ca2+ transients and Ca2+-binding proteins regulate physiological phenomena as diverse as muscle contraction, neurosecretion, and cell division. When Ca2+ is rapidly mixed with slow Ca2+ chelators, EGTA, or Mg2+/EDTA, artificial Ca2+ transients (ACTs) of varying duration (0.1-50 ms half-widths (hws)) and amplitude can be generated. We have exposed several Ca2+ indicators, Ca2+-binding proteins, and a Ca2+-dependent enzyme to ACTs of various durations and observed their transient binding of Ca2+, complex formation, and/or activation. A 0.1 ms hw ACT transiently occupied approximately 70% of the N-terminal regulatory sites of troponin C consistent with their rapid Ca2+ on-rate (8.7 +/- 2.0 x 10(7) M-1 s-1). A 1.1 ms hw ACT produced approximately 90% transient binding of the N-terminal of calmodulin (CaM) to the RS-20 peptide, but little binding of CaM's C-terminal to RS-20. A 0.6 ms hw ACT was sufficient for the N-terminal of CaM to transiently bind approximately 60% of myosin light chain kinase (MLCK), while a 1.8 ms hw ACT produced approximately 22% transient activation of the sarcoplasmic reticulum (SR) Ca2+/ATPase. In both cases, the ACT had fallen back to baseline approximately 10-30 ms before maximal binding of CaM to MLCK or SR Ca2+/ATPase activation occurred and binding and enzyme activation persisted long after the Ca transient had subsided. The use of ACTs has allowed us to visualize how the Ca2+-exchange rates of Ca2+-binding proteins dictate their Ca2+-induced conformational changes, Ca2+-induced protein/peptide and protein/protein interactions, and enzyme activation and inactivation, in response to Ca2+ transients of various amplitude and duration. By characterizing the response of these proteins to ACTs, we can predict with greater certainty how they would respond to natural Ca2+ transients to regulate cellular phenomena.
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Sinalização do Cálcio , Cálcio/metabolismo , Adenosina Trifosfatases/metabolismo , Sequência de Aminoácidos , Aminoquinolinas/metabolismo , Animais , Cálcio/fisiologia , Sinalização do Cálcio/efeitos dos fármacos , Calmodulina/metabolismo , Proteínas de Ligação a Calmodulina/metabolismo , Bovinos , Quelantes/farmacologia , Ácido Egtázico/metabolismo , Ácido Egtázico/farmacologia , Ativação Enzimática , Corantes Fluorescentes/metabolismo , Cinética , Substâncias Macromoleculares , Dados de Sequência Molecular , Quinase de Cadeia Leve de Miosina/metabolismo , Fragmentos de Peptídeos/metabolismo , Ligação Proteica , Retículo Sarcoplasmático/enzimologia , Espectrometria de Fluorescência , Troponina C/metabolismoRESUMO
PNU-87407 and PNU-88509, beta-ketoamide anthelmintics that are structurally related to each other and to the salicylanilide anthelmintic closantel, exhibit different anthelmintic spectra and apparent toxicity in mammals. The basis for this differential pharmacology was examined in experiments that measured motility and adenosine triphosphate (ATP) levels in larval and adult stages of the gastrointestinal nematode, Haemonchus contortus, and in a vertebrate liver cell line and mitochondria. PNU-87407 and PNU-88509 both exhibited functional cross-resistance with closantel in larval migration assays using closantel-resistant and -sensitive isolates of H. contortus. Each compound reduced motility and ATP levels in cultured adult H. contortus in a concentration- and time-dependent manner; however, motility was reduced more rapidly by PNU-88509, and ATP levels were reduced by lower concentrations of closantel than the beta-ketoamides. Tension recordings from segments of adult H. contortus showed that PNU-88509 induces spastic paralysis, while PNU-87407 and closantel induce flaccid paralysis of the somatic musculature. Marked differences in the actions of these compounds were also observed in the mammalian preparations. In Chang liver cells, ATP levels were reduced after 3 h exposures to > or = 0.25 microM PNU-87407, > or = 1 microM closantel or > or = 10 microM PNU-88509. Reductions in ATP caused by PNU-88509 were completely reversible, while the effects of closantel and PNU-87407 were irreversible. PNU-87407, closantel and PNU-88509 uncoupled oxidative phosphorylation in isolated rat liver mitochondria, inhibiting the respiratory control index (with glutamate or succinate as substrate) by 50% at concentrations of 0.14, 0.9 and 7.6 microM, respectively.
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Anti-Helmínticos/farmacologia , Haemonchus/efeitos dos fármacos , Mitocôndrias Hepáticas/efeitos dos fármacos , Salicilanilidas/farmacologia , Desacopladores/farmacologia , Trifosfato de Adenosina/metabolismo , Amidas , Animais , Anti-Helmínticos/administração & dosagem , Linhagem Celular , Relação Dose-Resposta a Droga , Feminino , Haemonchus/fisiologia , L-Lactato Desidrogenase/análise , Larva/efeitos dos fármacos , Larva/fisiologia , Mitocôndrias Hepáticas/metabolismo , Fosforilação Oxidativa , Ratos , Trichostrongylus/efeitos dos fármacos , Trichostrongylus/fisiologiaAssuntos
Neoplasias de Cabeça e Pescoço/diagnóstico por imagem , Recidiva Local de Neoplasia/diagnóstico por imagem , Tomografia Computadorizada de Emissão , Implantes Cocleares , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Tomografia Computadorizada por Raios X , Resultado do TratamentoRESUMO
Dihydroorotate dehydrogenase (DHODase) is the rate-limiting enzyme of the mammalian de novo pyrimidine biosynthesis pathway, and is the molecular target of the antiproliferative, immunosuppressive compound brequinar sodium (BQR). We have shown previously that the activity of the recombinant human enzyme displays pH and diethylpyrocarbonate sensitivities that implicate a critical role for one or more histidine residues in catalysis [Copeland et al., Arch Biochem Biophys 323: 79-86, 1995.]. Here we report the results of alanine scanning mutagenesis for each of the 8 histidine residues of the recombinant human enzyme. In most cases, the replacement of histidine by alanine had little effect on the Km values of the two substrates, dihydroorotate and ubiquinone, or on the overall kcat of the enzymatic reaction. Replacement of H71, H129, and H364 by alanine, however, completely abolished enzymatic activity. The loss of activity for the H71A mutant was unexpected, since this residue is not conserved in the homologous rat enzyme; in the rodent enzyme this residue is an asparagine. Replacement of H71 by asparagine in the human enzyme led to a full recovery of enzymatic activity, indicating that a histidine is not required at this position. Replacement of H26 by alanine led to about a 10-fold reduction in catalytic activity relative to the wild-type enzyme, with no significant perturbation of the substrate Km values. This mutant was, however, at least 167-fold less sensitive to inhibition by the noncompetitive inhibitor BQR. While the wild-type and other mutant enzymes displayed IC50 values for BQR inhibition between 6 and 10 nM, the H26A mutant was inhibited less than 25% at concentrations of BQR as high as 150 nM. These data suggest that H26 plays an important role in BQR binding to the enzyme.
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Antineoplásicos/farmacologia , Compostos de Bifenilo/farmacologia , Oxirredutases atuantes sobre Doadores de Grupo CH-CH , Oxirredutases/antagonistas & inibidores , Alanina , Sequência de Aminoácidos , Animais , Sequência de Bases , Di-Hidro-Orotato Desidrogenase , Histidina , Humanos , Dados de Sequência Molecular , Oxirredutases/química , Mutação Puntual , Ratos , Relação Estrutura-AtividadeRESUMO
To evaluate the effects of the in vivo endotoxin treatment of the rat on (1) the contractile responses in the subsequently isolated papillary muscle to adrenergic and cholinergic agonists and (2) the biochemical parameters (cyclic GMP, nitric oxide synthesis, protein phosphorylation and ADP-ribosyslation) in the subsequently isolated cardiomyocytes. Following the in vivo endotoxin treatment (4 mg/kg i.p., 18 h), contractile responses to increasing amounts of isoprenaline or to increasing amounts of oxotremorine in the presence of a fixed amount of isoprenaline were determined in isolated papillary strips. Activities of nitric oxide synthase, guanylyl cyclase, as well as phosphorylation of phospholamban and troponin-inhibitory subunit, and pertussis toxin-catalyzed and endogenous ADP-ribosylations were determined in the intact cardiomyocytes and subcellular fractions. The increase in the force of contraction by isoprenaline was reduced, while its inhibition by oxotremorine was greater in the endotoxin-treated papillary strips. The activities of both nitric oxide synthase, primarily of the inducible form of the enzyme, and cytosolic guanylyl cyclase were higher while the phosphorylations of both phospholamban and troponin-inhibitory subunit were of lesser magnitude in the cardiomyocytes following the in vivo endotoxin treatment. Pertussis toxin-catalyzed ADP-ribosylation of the 41 kDa polypeptide, which is the alpha subunit of Gi, was also decreased. The results of the present study support the postulate that alterations in both the cyclic AMP and cyclic GMP signalling cascade contribute to the myocardial dysfunction caused by endotoxin and cytokines.
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Adenosina Difosfato Ribose/metabolismo , GMP Cíclico/biossíntese , Coração/efeitos dos fármacos , Miocárdio/metabolismo , Óxido Nítrico/biossíntese , Toxina Pertussis , Fatores de Virulência de Bordetella/farmacologia , Animais , Cálcio/metabolismo , GMP Cíclico/metabolismo , Guanilato Ciclase/metabolismo , Homeostase , Masculino , Contração Miocárdica , Óxido Nítrico Sintase/metabolismo , Fosforilação , Ratos , Ratos Wistar , Receptores Adrenérgicos beta/metabolismo , Receptores Muscarínicos/metabolismoRESUMO
A novel cyclodepsipeptide of fungal origin, PF1022A, recently was reported to have anthelmintic activity. To supplement published reports and determine potential utility of PF1022A as a ruminant anthelmintic, the compound was examined in in vitro and in vivo models. Assays used measured motility of Haemonchus contortus (intrinsic drug potency), ATP levels (parasite death), and activity against H. contortus, Ostertagia ostertagi, and Trichostrongylus colubriformis in the jird (spectrum, potency, and efficacy by various routes). The potency of PF1022A in reducing motility is greater than commercial anthelmintics. Examination of ATP levels in PF1022A-paralyzed H. contortus indicates that worms are not killed, suggesting the compound acts as a neurotoxin in nematodes. In the jird, PF1022A has activity orally against each of the parasites studied and at doses comparable to all commercial anthelmintics, except the macrocyclic lactones which are more potent. Unfortunately, for some nematode species, parenteral delivery is ineffective at realistic doses.
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Anti-Helmínticos/uso terapêutico , Depsipeptídeos , Hemoncose/tratamento farmacológico , Peptídeos Cíclicos/uso terapêutico , Trifosfato de Adenosina/metabolismo , Administração Oral , Animais , Feminino , Gerbillinae , Haemonchus/efeitos dos fármacos , Estrutura Molecular , Ostertagia/efeitos dos fármacos , Trichostrongylus/efeitos dos fármacosRESUMO
This paper reports on 13 patients with a pain syndrome arising from the region of the greater cornu of the hyoid bone. It is often missed and yet is readily treatable. The syndrome causes pain on swallowing in the region of the hyoid which may radiate to the ear, face and lower jaw or may be felt also in the pharynx. Treatment by an injection of a mixture of depomedrone and one per cent lignocaine is very effective. The underlying pathology is discussed and it is suggested that in some cases the pain and discomfort experienced by patients may be due to tenosynovitis of the intermediate tendon of the digastric muscle. Greater recognition of this relatively common condition would not only result in more effective treatment but would also avoid unnecessary investigation and surgery.
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Osso Hioide , Dor/etiologia , Adulto , Idoso , Anti-Inflamatórios/uso terapêutico , Feminino , Humanos , Masculino , Metilprednisolona/análogos & derivados , Metilprednisolona/uso terapêutico , Acetato de Metilprednisolona , Pessoa de Meia-Idade , Pescoço , Dor/tratamento farmacológico , SíndromeRESUMO
A prospective study of 122 adults undergoing routine ear, nose and throat (ENT) operations over a three-month period was carried out to determine the cause of oropharyngeal trauma seen in some patients. Those having tonsillar or palatal surgery were excluded from the study. Forty-five (36.9 per cent) patients complained of a mild sore throat post-operatively and six (4.9 per cent) of a severe sore throat. Five of these (4 per cent) had evidence of injury to the uvula and soft palate which delayed their discharge from hospital. No single cause of trauma was identified but possible factors included the use of laryngeal masks (two cases), throat packs (two cases) and blind suctioning with a plastic Yankauer sucker (one case). There is a relatively high risk of oropharyngeal trauma during routine otolaryngological procedures and we recommend that care should be taken to prevent this common cause of significant post-operative morbidity.
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Complicações Intraoperatórias/etiologia , Orofaringe/lesões , Otorrinolaringopatias/cirurgia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Faringite/etiologia , Estudos Prospectivos , Fatores de Risco , Úvula/lesõesRESUMO
The roles of the 8 conserved cysteines and 1 arginine in the low molecular weight phosphotyrosyl protein phosphatases were investigated using site-directed mutagenesis of the recombinant bovine heart enzyme. Single mutants of cysteine to serine were studied for each cysteine; alanine replacements were also made for Cys-12, Cys-17, and Arg-18. The CD spectra of the purified proteins were effectively superimposable, consistent with the conclusion that no major structural alterations had occurred, but 1H NMR spectroscopy did reveal some spectral shifts in the aromatic region. Kinetic analysis of the mutant proteins demonstrated that only Cys-12, Cys-17, and Arg-18 had significantly altered catalytic activity toward the substrate p-nitrophenyl phosphate at pH 5. The Cys-12 and Arg-18 mutants were effectively inactive. Thus, it is concluded that Cys-12 is the catalytic nucleophile, and Arg-18 presumably serves an essential function in substrate binding. The C17S mutant had 6% residual activity compared with wild type protein, whereas the C17A mutant had 37% activity. Consistent with the observed activity of the Cys-17 mutant, a covalent phosphocysteine intermediate was trapped and identified by 31P NMR. Further kinetic analysis of C17A using several aryl phosphate monoester substrates with different leaving group pK alpha values indicated that no change in the rate-determining step of the catalytic mechanism had occurred, that is, dephosphorylation of the covalent phosphoenzyme intermediate remains rate-limiting. The C17A mutant had a 4-fold higher phosphate Ki and slightly higher Km values for p-nitrophenyl phosphate suggesting that Cys-17 may be important for optimal positioning of the substrate phosphate moiety.