Studies of the Co2+-Activated Ribulose-1, 5-Bisphosphate Carboxylase/Oxygenase by the Use of Spectrophotometry
Transient absorption bands are formed upon addition of ribulose-l,5-bisphosphate (RuBP) to the Co2+ -activated ribulose-1,5-bisphosphate carboxylase/oxygenase, RubisCO. In the visible region the prominent absorption band during steady state has a maximum at 610 nm. Stopped flow technique was used to study the increase in absorbance at this wavelength and two distinct phases in the progress curve for the approach to steady state absorbance were observed. The rates for these two phases, respectively, were similar to those found earlier for the two enzyme-Co2+ abound intermediates using EPR technique (1). It is therefore proposed that most of the transient optical absorption originates from an enzyme-Co2+ -coordinated RuBP molecule and an enzyme-Co2+ -coordinated enediolate anion of it, where bound RuBP appears first. Furthermore, the most rapid phase in the progress curve is a first order reaction, independent of the concentration of RuBP. This indicates that the formation of enzyme-Co2+ -coordinated RuBP is preceeded by another reaction in which RuBP binds to the enzyme, probably without metal coordination.
KeywordsOptical Absorption Spectrum First Order Reaction Progress Curve Metal Coordination Stop Flow Technique
Unable to display preview. Download preview PDF.
- 12.Andréasson L-E, Bränden B., Malmström B.G., Strömberg C. & Vänngard T., “Oxidases and Related Redox Systems”, pp.87–95, 1973, University Park Press, BaltimoreGoogle Scholar