One of the proteinases
produced was an extracellular prolyl endopeptidase. A similar,
intracellular, protein with only a slight difference in isoelectric
point, was purified from fruit bodies (Sattar et al., 1990).
Intracellular proteinases may be functional during maturation
or post-harvest sporophore development. From fresh mature
fruit bodies of A. bisporus an enzyme active against bradykinin
was purified (Kizuki & Moriya, 1982). Enzyme inhibition
experiments indicated that this enzyme is probably a cysteine
proteinase. From the stipes of post-harvest A. bisporus
mushrooms Burton et al. (1993) purified a serine proteinase
and the corresponding gene was cloned (Kingsnorth,
Woodhouse & Burton, 1997). Proteinase activity is strongly
increased in post-harvest mushrooms possibly for recycling
amino acids for the nutritionally starved mushroom and}or to
activate other degrading enzymes.