Am. Creighton et al., THE STROMAL PROCESSING PEPTIDASE ACTIVITIES FROM CHLAMYDOMONAS-REINHARDTII AND PISUM-SATIVUM - UNEXPECTED SIMILARITIES IN REACTION SPECIFICITY, Plant molecular biology, 23(6), 1993, pp. 1291-1296
We have partially purified the stromal processing peptidase from Chlam
ydomonas reinhardtii and compared the properties of this activity with
those of the pea counterpart. Whereas previous studies have suggested
that the two enzymes may have significantly different reaction specif
icities, we find that they are in fact very similar. Both enzymes proc
ess precursors of two higher-plant thylakoid lumen proteins, and one C
. reinhardtii lumenal protein, to similar intermediate-size forms. How
ever, whereas the algal enzyme processes the precursor of C. reinhardt
ii Rubisco small subunit to the correct mature size, this precursor is
cleaved only to an intermediate size by the pea enzyme. The small sub
unit precursor from pea appears to be cleaved by both enzymes in a sim
ilar manner. In terms of sensitivity to inhibitors, the two activities
are notably different; the pea enzyme has previously been shown to be
inhibited by several types of heavy-metal chelator, but we have found
that none of these compounds affect the algal activity.