The mechanism of deuterium oxide-induced protein degradation in Lemna minor.

Transfer of Lemna minor fronds to culture medium containing 50% (v/v) deuterium oxide induces a large increase in the rate of protein breakdown, which is not due to an increase in the activity of acidic or neutral proteolytic enzymes or peptidases. Biochemical and ultrastructural evidence indicates that deuterium oxide affects the properties of certain membranes, particularly the tonoplast, and allows vacuolar proteolytic enzymes to pass into the cytoplasm and cause the increased protein breakdown.