RESUMO
Proteinase A from Aspergillus niger var. macrosporus is a non-pepsin-type acid proteinase distinctly different in various properties from the family of pepsin-type aspartic proteinases, and so far it remains unknown which residues participate in the catalysis of the enzyme and how the mechanism operates. The acid proteinase A was crystallized from an ammonium sulfate solution by the hanging-drop vapor diffusion method. The space group of the crystals was P2(1)2(1)2(1) with unit cell dimensions of a = 54.7 A, b = 70.4 A and c = 38.0 A. On the assumption that there is one enzyme molecule in the asymmetric unit, the calculated ratio of volume to unit protein mass (Vm) was 1.64 A3 per dalton. Diffraction data were collected up to a resolution higher than 1.5 A, using the Weissenberg camera for macromolecular crystallography with synchrotron radiation. The crystal of proteinase A is, therefore, suitable for the structural analysis with a high resolution.
Assuntos
Ácido Aspártico Endopeptidases/química , Aspergillus/enzimologia , Cristalografia , Conformação Proteica , Difração de Raios XRESUMO
Proteinase A from Aspergillus niger var. macrosporus is a non-pepsin-type acid proteinase, whose catalytic residues and mechanism remain to be elucidated. A new form of proteinase A crystals more suitable for crystallography than that obtained previously was prepared from an ammonium sulfate solution at pH 3.5 by the hanging-drop vapor diffusion method. The space group of the crystals was P2(1)2(1)2(1), with unit cell dimensions of a = 69.75 +/- 0.06 A, b = 87.55 +/- 0.05 A, and c = 60.83 +/- 0.04 A. On the assumption of two enzyme molecules per asymmetric unit, the calculated volume to unit protein mass ratio (Vm) was 2.08 A3/Da. By assuming the specific volume to be 0.74 cm3/g, the solvent content (Vso1) was estimated to be 41%, i.e., much larger than that of the crystal form obtained previously at pH 2.0 (Vso1 = 26%). Diffraction data were collected up to a resolution higher than 1.6 A, using the Weissenberg camera for macromolecular crystallography with synchrotron radiation.
Assuntos
Ácido Aspártico Endopeptidases/química , Aspergillus niger/enzimologia , Sulfato de Amônio , Cristalização , Cristalografia por Raios X , Difusão , Concentração de Íons de HidrogênioAssuntos
Ácido Aspártico Endopeptidases/química , Aspergillus niger/enzimologia , Conformação Proteica , Sequência de Aminoácidos , Ácido Aspártico Endopeptidases/isolamento & purificação , Ácido Aspártico Endopeptidases/metabolismo , Sítios de Ligação , Cromatografia em Gel , Cromatografia por Troca Iônica , Dipeptídeos/farmacologia , Substâncias Macromoleculares , Espectroscopia de Ressonância Magnética , Dados de Sequência Molecular , Pepsina A/química , Inibidores de Proteases/química , Inibidores de Proteases/metabolismoAssuntos
Ácido Aspártico Endopeptidases/antagonistas & inibidores , Aspergillus niger/enzimologia , Pepstatinas/farmacologia , Sequência de Aminoácidos , Ácido Aspártico Endopeptidases/química , Precursores Enzimáticos/química , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Dados de Sequência Molecular , Estrutura Molecular , Conformação Proteica , Relação Estrutura-AtividadeRESUMO
Magnetite prepared by an enzyme-dependent reaction gradually released iron ion into the acidic-to-neutral buffer solution. A preparatory experiment was performed to examine the efficiency of magnetite as an iron supplement. Feeding exsanguinated rats with being magnetite resulted in the hematocrit value being recovered without any serious adverse effect on the digestive organs.