Prosaposin (Proactivator polypeptide) [Cleaved into: Saposin-A (Protein A); Saposin-B-Val; Saposin-B (Cerebroside sulfate activator) (CSAct) (Dispersin) (Sphingolipid activator protein 1) (SAP-1) (Sulfatide/GM1 activator); Saposin-C (A1 activator) (Co-beta-glucosidase) (Glucosylceramidase activator) (Sphingolipid activator protein 2) (SAP-2); Saposin-D (Component C) (Protein C)]
1_MYALF 6_ LLASL 11_ LGAAL 16_ AGPVL 21_ GLKEC 26_ TRGSA 31_ VWCQN 36_ VKTAS 41_ DCGAV 46_ KHCLQ 51_ TVWNK 56_ PTVKS 61_ LPCDI 66_ CKDVV 71_ TAAGD 76_ MLKDN 81_ ATEEE 86_ ILVYL 91_ EKTCD 96_ WLPKP 101_ NMSAS 106_ CKEIV 111_ DSYLP 116_ VILDI 121_ IKGEM 126_ SRPGE 131_ VCSAL 136_ NLCES 141_ LQKHL 146_ AELNH 151_ QKQLE 156_ SNKIP 161_ ELDMT 166_ EVVAP 171_ FMANI 176_ PLLLY 181_ PQDGP 186_ RSKPQ 191_ PKDNG 196_ DVCQD 201_ CIQMV 206_ TDIQT 211_ AVRTN 216_ STFVQ 221_ ALVEH 226_ VKEEC 231_ DRLGP 236_ GMADI 241_ CKNYI 246_ SQYSE 251_ IAIQM 256_ MMHMQ 261_ PKEIC 266_ ALVGF 271_ CDEVK 276_ EMPMQ 281_ TLVPA 286_ KVASK 291_ NVIPA 296_ LELVE 301_ PIKKH 306_ EVPAK 311_ SDVYC 316_ EVCEF 321_ LVKEV 326_ TKLID 331_ NNKTE 336_ KEILD 341_ AFDKM 346_ CSKLP 351_ KSLSE 356_ ECQEV 361_ VDTYG 366_ SSILS 371_ ILLEE 376_ VSPEL 381_ VCSML 386_ HLCSG 391_ TRLPA 396_ LTVHV 401_ TQPKD 406_ GGFCE 411_ VCKKL 416_ VGYLD 421_ RNLEK 426_ NSTKQ 431_ EILAA 436_ LEKGC 441_ SFLPD 446_ PYQKQ 451_ CDQFV 456_ AEYEP 461_ VLIEI 466_ LVEVM 471_ DPSFV 476_ CLKIG 481_ ACPSA 486_ HKPLL 491_ GTEKC 496_ IWGPS 501_ YWCQN 506_ TETAA 511_ QCNAV 516_EHCKR
1: Saposin-A and saposin-C stimulate the hydrolysis of glucosylceramide by beta-glucosylceramidase (EC 3.2.1.45) and galactosylceramide by beta-galactosylceramidase (EC 3.2.1.46). Saposin-C apparently acts by combining with the enzyme and acidic lipid to form an activated complex, rather than by solubilizing the substrate
2: Saposin-B stimulates the hydrolysis of galacto-cerebroside sulfate by arylsulfatase A (EC 3.1.6.8), GM1 gangliosides by beta-galactosidase (EC 3.2.1.23) and globotriaosylceramide by alpha-galactosidase A (EC 3.2.1.22). Saposin-B forms a solubilizing complex with the substrates of the sphingolipid hydrolases
3: Saposin-D is a specific sphingomyelin phosphodiesterase activator (EC 3.1.4.12)
4: Behaves as a myelinotrophic and neurotrophic factor, these effects are mediated by its G-protein-coupled receptors, GPR37 and GPR37L1, undergoing ligand-mediated internalization followed by ERK phosphorylation signaling
5: Saposins are specific low-molecular mass non-enzymic proteins, they participate in the lysosomal degradation of sphingolipids, which takes place by the sequential action of specific hydrolases