title: The thermal stability of a castor bean seed acid phosphatase.
abstract: The effect of temperature on the activity and structural stability of an acid phosphatase (EC 3.1.3.2.) purified from castor bean (Ricinus communis L.) seeds have been examined. The enzyme showed high activity at 45 degrees C using p-nitrophenylphosphate (p-NPP) as substrate. The activation energy for the catalyzed reaction was 55.2 kJ mol(-1) and the enzyme maintained 50% of its activity even after 30 min at 55 degrees C. Thermal inactivation studies showed an influence of pH in the loss of enzymatic activity at 60 degrees C. A noticeable protective effect from thermal inactivation was observed when the enzyme was preincubated, at 60 degrees C, with the reaction products inorganic phosphate-P (10 mM) and p-nitrophenol-p-NP(10 mM). Denaturation studies showed a relatively high transition temperature (Tm) value of 75 degrees C and an influence of the combination of Pi (10 mM) and p-NP (10 mM) was observed on the conformational behaviour of the macromolecule.
authors.affiliation: Departamento de Bioquímica, Instituto de Biologia, Universidade Estadual de Campinas, São Paulo, Brazil.
authors.forename: Paulo Afonso
authors.initials: PA
authors.lastname: Granjeiro
authors.forename: Alexandre Donizeti Martins
authors.initials: AD
authors.lastname: Cavagis
authors.forename: Luciana
authors.initials: L
authors.lastname: de Campos Leite
authors.forename: Carmen Veríssima
authors.initials: CV
authors.lastname: Ferreira
authors.forename: José Mauro
authors.initials: JM
authors.lastname: Granjeiro
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Aoyama
mesh_terms: D000135:Acid Phosphatase / Q000737:chemistry*; D002367:Ricinus communis / Q000201:enzymology*; D004795:Enzyme Stability; D006358:Hot Temperature; D009596:Nitrophenols / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry*; D011489:Protein Denaturation; D012639:Seeds / Q000201:enzymology*; D013816:Thermodynamics
chemical_list: D009596:Nitrophenols; D009943:Organophosphorus Compounds; D010710:Phosphates; D010940:Plant Proteins; C008644:nitrophenylphosphate; D000135:Acid Phosphatase