<P> CD - MPR </P> <P> When the CD - MPR is knocked out in mice we observe mice that appear healthy apart from the fact that they have defects in the targeting of multiple lysosomal enzymes . These mice display elevated levels of phosphorylated lysosomal enzymes in their blood and they accumulate undigested material in their lysosomes . </P> <P> From these knockout mice we can deduce that both receptors are needed for the efficient targeting of lysosomal enzymes . If we compare the lysosomal enzymes that are secreted by the two different knockout cell lines we see different sets of enzymes . This suggests that each MPR interacts preferentially with a subset of lysosomal enzymes . </P> <P> The CI - MPR and CD - MPR are structurally distinct receptors however they share an overall general structure as they are both type I integral membrane proteins . Both receptors have a large N - terminal extracytoplasmic domain, one transmembrane domain and a short C - terminal cytoplasmic tail . These cytoplasmic tails contain multiple sorting signals; some of which can be either phosphorylated or palmitoylated . </P>

Mannose 6 phosphate dependent pathway for routing lysosomal enzymes can be blocked by