Collect. Czech. Chem. Commun. 1984, 49, 1543-1551

S-adenosine-L-homocysteine hydrolase from Nicotiana tabacum L.: Isolation and properties

Ladislava Šebestová, Ivan Votruba and Antonín Holý

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague


S-Adenosyl-L-homocysteine hydrolase (E.C. (SAH hydrolase) from an explanate culture of Nicotiana tabacumL. was purified to homogeneity. The enzyme is composed of four subunits of molecular weight of 55 000. The native molecule of final molecular weight of 220 000 aggregates in solution to multimers of molecular weight of 440 000 and higher. When subjected to isoelectric focusing the enzyme yields two components of equal distribution and pI-values of 5.15 and 5.25. The enzyme is thermolabile and is readily inactivated at temperatures above 3 °C. The KM value for adenosine is 5.15 μmol l-1 and for S-adenosyl-L-homocysteine (SAH) 11 μmol l-1. The temperature optimum of both SAH synthesis and hydrolysis is 37 °C, the pH optimum of SAH hydrolysis is 8.0, of SAH synthesis 7.14. The enzyme is competitively inhibited by (S)-9-(2,3-dihydroxypropyl)adenine and inactivated by both enantiomers of eritadenine and 3-(adenin-9-yl)-2-hydroxypropionic acid.