28] Cell-free components in dinoflagellate bioluminescence. The particulate activity: Scintillons; the soluble components: Luciferase, luciferin, and luciferin-binding protein

Abstract

This chapter discusses the cell-free components in dinoflagellate bioluminescence, and describes the particulate activity of scintillons; and the soluble components of luciferase, luciferin, and luciferin-binding protein. The activity of scintillons is assayed by measuring the light emission following the rapid injection of acid (by syringe) or mixing (by stopped flow) of the sample at pH 8 with acid to bring the final pH to about 5.7. The active luciferase in the soluble fraction of extracts of G. polyedra may occur in two different molecular weight forms. The larger is a 135,000 MW molecule, the native single chain, which occurs in extracts made at pH 8. If, instead, the extract is made with a buffer at pH 6, all of the activity is found in the 35,000 MW range, this due to the action of a protease. Luciferin (LFN) is assayed by one of three methods. Routine determinations are m a d e by adding a small volume (less than 100 μl) of LFN to a fixed given amount (usually 5 or 10 μl) of Lase (either A135 or B35) in 2 ml of assay buffer (pH 6.3) at 20°.