Binding of inactivated tyrosine aminotransferase to microsomal membranes.

Tyrosine aminotransferase from guinea pig liver spontaneously inactivates both in crude homogenates and in tissue slices. In the course of inactivation the cytosolic enzyme progressively translocates only into the microsomal fraction under an inactive form. Translocated enzyme activity can be restored by dithiothreitol addition which also produces the release of the enzyme from the microsomal particles. The specific binding of tyrosine aminotransferase to microsomal particles as a critical event for subsequent proteolytic degradation of the enzyme is postulated.