Intracellular localization of two molecular forms of membrane acid protease in Aspergillus oryzae.

The intracellular localization of two forms of membrane-bound acid protease (M1 and M2) [EC 3.4.23.6] of Aspergillus oryzae (Tsujita, Y. & Endo, A. (1978) Eur. J. Biochem. 84, 347-353) was investigated. When the mycelia were treated with wall-lytic enzymes, M2 remained in the cells but most of M2 was solubilized and released. The cell wall fraction obtained by mechanical disruption of the mycelia contained less than 5% of the total acid protease activity in the cells. Subcellular fractionation of the membranes obtained from burst spheroplasts showed that the acid protease was present in both rough and smooth microsomes. Acid protease M1 was predominant in the former and M2 in the latter, possibly on the surface of the cytoplasmic membranes.