The native molecular size of alkyl-dihydroxyacetonephosphate synthase and dihydroxyacetonephosphate acyltransferase.
Dihydroxyacetonephosphate acyltransferase (DHAP-acyltransferase) and alkyl-dihydroxyacetonephosphate synthase (alkyl-DHAP synthase) are the first two enzymes involved in the biosynthesis of ether phospholipids. Both peroxisomal enzymes have recently been purified to homogeneity and their molecular weights under denaturing conditions were reported. To determine the in situ functional size of both enzymes, radiation inactivation experiments were performed. Alkyl-DHAP synthase showed single exponential decays, both when enzymatic activity and when immunoreactive protein levels were measured, from which target sizes of 79+/-2 kDa and 78+/-4 kDa, respectively, were calculated. DHAP-acyltransferase activity increased at lower doses and decayed upon further irradiation with an apparent target size of 62+/-7 kDa. We conclude from these data that the functional unit sizes for both enzymes in situ are represented by their single polypeptide chains.
Department of Biochemistry of Lipids, Centre for Biomembranes and Lipid Enzymology, Institute for Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
J
J
Biermann
K
K
Schoonderwoerd
M L
ML
Hom
L H
LH
Luthjens
H
H
Van den Bosch
D000201:Activation Analysis; D000217:Acyltransferases / Q000737:chemistry*; D019883:Alkyl and Aryl Transferases / Q000737:chemistry*; D000818:Animals; D006168:Guinea Pigs; D008099:Liver / Q000201:enzymology*; D008565:Membrane Proteins / Q000737:chemistry*; D008830:Microbodies / Q000201:enzymology; D008970:Molecular Weight
D008565:Membrane Proteins; D000217:Acyltransferases; C020051:glycerone-phosphate O-acyltransferase; D019883:Alkyl and Aryl Transferases; C019654:alkylglycerone-phosphate synthase