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Kinetic properties of ribulose 1,5-bisphosphate carboxylase/oxygenase from Anabaena variabilis

1980; Elsevier BV; Volume: 201; Issue: 1 Linguagem: Inglês

10.1016/0003-9861(80)90509-3

1096-0384

Murray R. Badger,

Hemoglobin structure and function

Ribulose 1,5-biphosphate carboxylase/oxygenase was purified from the blue-green algae Anabaena variabilis and the kinetic properties of this enzyme were studied in an attempt to compare them with values measured for higher plant enzyme. Major contrasting differences in the kinetic responses of the Anabaena enzyme appear to be the following: (l)The Km(CO2) is some 10-fold or more higher; (2) the Kc·KMg value for activation of the enzyme with CO2 and Mg2+ is also increased 10-fold or more; (3) the maximum turnover rate per active site for the carboxylase reaction 3- to 4-fold higher; (4) the Ki(O2) of oxygen in the carboxylase reaction is 2- to 3-fold higher as is the Km(O2) for the oxygenase reaction; (5) the ratio of V carboxylase to V oxygenase may also be increased; (6) the pH responses of V carboxylase and Km(CO2) are different in the pH range below 7.5. These differences are considered in terms of the possible evolutionary changes which have taken place in the enzyme to increase affinity for CO2 in carboxylation and reduce oxygen inhibition of carboxylation in vivo.