The localisation of 2-carboxy-D-arabinitol 1-phosphate and inhibition of Rubisco in leaves of Phaseolus vulgaris L.

A recent controversial report suggests that the nocturnal inhibitor of Rubi sco, 2-carboxy-D-arabinitol 1-phosphate (CA1P), does not bind to Rubisco in vivo and therefore that CA1P has no physiological relevance to photosynthe tic regulation. It is now proved that a direct rapid assay can be used to d istinguish between Rubisco-bound and free CA1P, as postulated in the contro versial report. Application of this direct assay demonstrates that CA1P is bound to Rubisco in vivo in dark-adapted leaves. Furthermore, CA1P is shown to be in the chloroplasts of mesophyll cells, Thus, CA1P does play a physi ological role in the regulation of Rubisco, (C) 1999 Federation of European Biochemical Societies.