The extractability of chlorophyllase is used as an indicator for the way in which the enzyme is incorporated in Phaeodactylum tricomutum photosynthetic membranes. Whereas with various aqueous solutions no appreciable amount of chlorophyllase is washed from the membranes even after chloroform-pretreatment, the enzyme can be extracted with aqueous solutions after practically all the lipids have been removed by means of 80% acetone.The proteins in an aqueous extract of the membranes thus treated were separated by electrophoresis on a 4% polyacrylamide gel; extraction of the active protein from several gels yielded a purified chlorophyllase solution.As with the intramembraneous enzyme, activity of purified, solubilized chlorophyllase depends upon the combined presence of MgClj and dithiothreitol. The enzyme is inactivated upon heating at 56°C for 5 min.After SDS gel-electrophoresis of an enriched extract, enzyme activity could be localized in the gels. The molecular weight of SDStreated chlorophyllase, or of its principal subunit, was estimated to be about 38 kilodaltons.The results are discussed in terms of the identity of prochlorophyllase. WILLEMKE TERPSTRA Physiol. Plant. 44. 1978
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