ASPH Human

ASPH hydroxylates an Asp or Asn residue in EGF domains. ASPH is involved in calcium homeostasis. ASPH is expressed from two promoters and goes through extensive alternative splicing. The encoded set of ASPH proteins share varying quantities of overlap near their N-termini although have considerable differences in their C-terminal domains resulting in distinct functional properties. The longest isoforms (a and f) include a C-terminal Aspartyl/Asparaginyl beta-hydroxylase domain that hydroxylates aspartic acid or asparagine residues in the EGF domain, including protein C, coagulation factors VII, IX, and X, and the complement factors C1R and C1S. Further isoforms diverge mainly in the C-terminal sequence and lack the hydroxylase domain, and some have been localized to the endoplasmic and sarcoplasmic reticulum.