Localization of alpha-Amylase in the Apoplast of Pea (Pisum sativum L.) Stems.

Most of the activity of an alpha-amylase present in crude pea (Pisum sativum L. cv Laxton's Progress No. 9) leaf preparations cannot be found in isolated pea leaf protoplasts. The same extrachloroplastic alpha-amylase is present in pea stems, representing approximately 6% of total stem amylolytic activity and virtually all of the alpha-amylase activity. By a simple infiltration-extraction procedure, the majority (87%) of this alpha-amylase activity was recovered from the pea stem apoplast without significantly disrupting the symplastic component of the tissue. Only 3% of the beta-amylase activity and less than 2% of other cellular marker enzymes were removed during infiltration-extraction.