期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1991
卷号：88
期号：9
页码：4020-4024
DOI：10.1073/pnas.88.9.4020
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：cDNAs for glutathione-independent prostaglandin D synthase were isolated from cDNA libraries of human brain. The longest cDNA insert was 837 base pairs long and contained a coding region of 570 base pairs corresponding to 190 amino acid residues with a calculated Mr of 21,016. Between two cDNA inserts isolated from the two different libraries, nucleotide substitutions were observed at 16 positions, including conservative amino acid substitutions at 2 positions and nonconservative substitutions at 5 positions, indicating genetic heterogeneity of this enzyme in humans. The computer-assisted homology search revealed that the enzyme is a member of the lipocalin superfamily, comprising secretory hydrophobic molecule transporters, showing the greatest homology (28.8-29.4% identity; 51.3-53.1% similarity) to alpha 1-microglobulin among the members of this superfamily. In a phylogenetic tree of the superfamily, this enzyme, alpha 1-microglobulin, and the gamma chain of the complement component C8 form a cluster separate from the other 14 members. The two distinctive characteristics of glutathione-independent prostaglandin D synthase, as compared to the other members of this superfamily, are its enzymatic properties and its association with membranes that were probably acquired after evolutionary divergence of the two lipocalins. Based on the observed sequence homology, the tertiary structure of the enzyme was deduced to consist of an eight-stranded anti-parallel beta-barrel forming a hydrophobic pocket. Furthermore, the Cys-65 residue in the pocket, which is conserved only in the human and rat enzymes but not in other lipocalins, was considered to be a putative active site of the enzyme.
