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Intracellular localization of two molecular forms of membrane acid protease in Aspergillus oryzae
Abstract:
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.
Insights
This study investigated the location of two Aspergillus oryzae acid proteases (M1 and M2). Most M2 was released from cells, while M1 and M2 were found in cellular membranes, likely on the cytoplasmic surface.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Aspergillus oryzae produces membrane-bound acid proteases (M1 and M2) with EC 3.4.23.6.
- Understanding enzyme localization is crucial for elucidating cellular functions.
Purpose of the Study:
- To determine the intracellular localization of Aspergillus oryzae membrane-bound acid proteases M1 and M2.
- To investigate the distribution of these proteases within cellular compartments.
Main Methods:
- Treatment of Aspergillus oryzae mycelia with wall-lytic enzymes.
- Mechanical disruption of mycelia to obtain cell wall fractions.
- Subcellular fractionation of membranes from burst spheroplasts.
- Analysis of acid protease activity in different cellular fractions.
Main Results:
- Most M2 protease was solubilized and released from mycelia treated with wall-lytic enzymes.
- Cell wall fractions contained less than 5% of total acid protease activity.
- Acid proteases M1 and M2 were found in both rough and smooth microsomes.
- M1 was predominant in rough microsomes, and M2 in smooth microsomes, suggesting localization on cytoplasmic membranes.
Conclusions:
- Aspergillus oryzae acid proteases M1 and M2 are primarily associated with intracellular membranes, not the cell wall.
- M1 and M2 exhibit differential localization within microsomal fractions, potentially on the cytoplasmic membrane surface.