Marine Biology

, Volume 36, Issue 3, pp 199–206

Photosynthetic carboxylating enzymes in Phaeodactylum tricornutum: Assay methods and properties

  • D. Mukerji
  • I. Morris
Article

Abstract

Rapid freezing (in liquid nitrogen) of the marine diatom Phaeodactylum tricornutum Bohlin followed by thawing permits a convenient and sensitive measurement of the activities of carboxylating enzymes without the need to prepare a cell-free extract. Using this method, the properties of RuDP and PEP carboxylases have been compared with those assayed in cell-free extracts. The most significant difference was in the Michaelis' constants (Km's); the values being lower in the freeze/thaw assay. The absolute rate of carbon-dioxide fixation by the enzymes was less than the rate of photosynthesis by the intact alga. Significantly, the activity of PEP carboxylase was comparable (in some experiments, greater) to that of RuDP carboxylase. The significance of this and the possibility of an enzymatic approach to measurements of marine primary productivity are discussed.

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Copyright information

© Springer-Verlag 1976

Authors and Affiliations

  • D. Mukerji
    • 1
    • 2
  • I. Morris
    • 1
  1. 1.Bigelow Laboratory for Ocean SciencesWest Boothbay HarborUSA
  2. 2.Department of Botany and MicrobiologyUniversity College LondonLondonEngland

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