Two classes of proteinases have been identified in the differentiating cellular slime mold, Dictyostelium discoideum. Previous studies have suggested that these two classes of enzymes are localized in two separate types of lysosomes that may serve separate metabolic functions. Based on precedences established from studies of higher animal systems, it has been postulated that D. discoideum cells may use two different membrane receptor systems for transferring proteinases to the two types of lysosomes. In this project isopycnic centrifugation experiments, employing Percoll density gradients, will be performed in attempting to resolve the two types of lysosomes from cell homogenates. Separate studies will focus on 1) identifying receptor systems that function in regulating the compartmentations of proteinases, and 2) identifying specific sugars or sugar-phosphate residues in the proteinases that interact with these receptor systems. Subsequent experiments will be directed towards evaluating whether one subpopulation on lysosomes in D. discoideum may serve a unique role in catalyzing the degradation of soluble cell enzymes during differentiation.