RESUMO
Mammalian and plant purple acid phosphatases have similar active site structures despite low sequence identity (<20%). Although no bacterial enzyme has been purified, a sequence database search revealed that genes that could encode potential purple acid phosphatases may be restricted to a small number of organisms (i.e. myco- and cyanobacteria). Analysis of their deduced amino acid sequences and predicted secondary structures indicates that the cyanobacterial enzyme is similar to both the mammalian and the recently discovered low-molecular-weight plant purple acid phosphatases, while the mycobacterial enzyme is homologous to the fungal and high-molecular-weight plant purple acid phosphatases. Homology models indicate that both bacterial proteins appear to be similar to mammalian purple acid phosphatases in the immediate vicinity of the active site. It is likely that these enzymes act as Fenton-type catalysts in order to prevent damage caused by reactive oxygen species generated by invaded host cells (M. tuberculosis) or by the light-harvesting complex (Synechocystis sp.).
Assuntos
Fosfatase Ácida/genética , Bactérias/enzimologia , Glicoproteínas/genética , Fosfatase Ácida/química , Sequência de Aminoácidos , Animais , Bactérias/genética , Cianobactérias/enzimologia , Cianobactérias/genética , Fabaceae/enzimologia , Fabaceae/genética , Glicoproteínas/química , Mamíferos/genética , Dados de Sequência Molecular , Mycobacterium tuberculosis/enzimologia , Mycobacterium tuberculosis/genética , Plantas/enzimologia , Plantas/genética , Plantas Medicinais , Conformação Proteica , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , SuínosRESUMO
EDTA-soluble material, extracted from incisor teeth of rats given 50 ppm fluoride (NaF) in drinking water ad libitum from conception to age nine wk, contained significantly higher levels of protein (P less than 0.01) and gamma-carboxyglutamic acid (P less than 0.01) than did similar material from control rats. Tooth fluoride levels indicated that the incisors were mildly fluorosed. Analysis of these data indicates that mild fluorosis of rat incisor teeth involves not only the characteristic disturbances of pigmentation and mineral structure but also some alteration of the matrix protein.