Chloroplast subfractions were monitored for sodium dodecyl sulfate-sta
ble proteases. Nine distinct activities in the molecular mass range fr
om 14 to 66 kD have been detected. Five of the proteases associated wi
th thylakoid membranes belong to the serine and cysteine types of prot
eases. These activities could be preserved and purified by a two-step
electrophoresis procedure.