Stability of alkyl-dihydroxyacetonephosphate synthase in human control and peroxisomal disorder fibroblasts.
Alkyl-dihydroxyacetonephosphate synthase (alkyl-DHAP synthase) is a peroxisomal enzyme that plays a key role in ether phospholipid biosynthesis. To determine the turnover of alkyl-DHAP synthase in several peroxisomal disorders, pulse-chase experiments were performed. In control fibroblasts, mature alkyl-DHAP synthase displayed a half-life of 23 +/- 12 h. In Zellweger syndrome and rhizomelic chondrodysplasia punctata fibroblast cell lines, in which alkyl-DHAP synthase cannot be imported into peroxisomes, the enzyme was mainly detected in its precursor form. This precursor form showed a much shorter half-life, 5 +/- 2 h. In contrast, when the precursor protein accumulated inside the peroxisome of a particular neonatal adrenoleukodystrophy cell line in which processing does not take place, a half-life of 18 +/- 8 h, resembling that of the mature protein in controls, was observed. In a cell line from a patient with a single deficiency in the activity of alkyl-DHAP synthase, the mature form was detected and its radioactivity decreased with a half-life of 16 +/- 7 h. Collectively, these results provide an explanation for the instability of alkyl-DHAP synthase outside its target organelle. Additionally, they indicate that both the precursor and mature form of alkyl-DHAP synthase exhibit considerable intraperoxisomal turnover.
Biermann
J
J
Centre for Biomembranes and Lipid Enzymology, Utrecht University, The Netherlands.
Gootjes
J
J
Wanders
R J
RJ
van den Bosch
H
H
D019883:Alkyl and Aryl Transferases / Q000096:biosynthesis / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004792:Enzyme Precursors / Q000096:biosynthesis / Q000378:metabolism; D004795:Enzyme Stability; D005347:Fibroblasts / Q000201:enzymology*; D006207:Half-Life; D006801:Humans; D008715:Methionine / Q000378:metabolism; D018901:Peroxisomal Disorders / Q000201:enzymology* / Q000473:pathology; D011233:Precipitin Tests; D013462:Sulfur Radioisotopes
D004792:Enzyme Precursors; D013462:Sulfur Radioisotopes; D008715:Methionine; D019883:Alkyl and Aryl Transferases; C019654:alkylglycerone-phosphate synthase; D003545:Cysteine