The overall objectives of the project are to examine the role that catheptic proteases and other acid hydrolases play in the turnover of specific cellular enzymes and proteins during synchronous vegetative growth and gametic differentiation in the unicellular eukaryote Chlamydomonas reinhardtii. Apart from ascertaining the function of multiple forms of cathepsin D known to occur in this organism, other lysosomal enzymes will be isolated and purifed, and their ability to degrade specific proteins and nucleic acids studied. Lysosomal vesicles will be isolated from different stages of cell development and their hydrolytic enzyme content assayed. The transport of substrates into these vesicles and the degradation of natural purified protein substrates will be studied.