A second isoform of 3-ketoacyl-CoA thiolase found in Caenorhabditis elegans, which is similar to sterol carrier protein x but lacks the sequence of sterol carrier protein 2

European Journal of Biochemistry Volume 245 Issue 2 Page 252-259 published_at 1997
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Title ( eng )
A second isoform of 3-ketoacyl-CoA thiolase found in Caenorhabditis elegans, which is similar to sterol carrier protein x but lacks the sequence of sterol carrier protein 2
Creator
Bun-ya Masanori
Maebuchi Motohiro
Hashimoto Takeshi
Yokota Sadaki
Kamiryo Tatsuyuki
Source Title
European Journal of Biochemistry
Volume 245
Issue 2
Start Page 252
End Page 259
Abstract
We cloned a full-length cDNA of the nematode Caenorhabditis elegans that encodes a 44-kDa protein (P-44, 412 residues) similar to sterol carrier protein x (SCPx). Mammalian SCPx is a bipartite protein: its 404-residue N-terminal and 143-residue C-terminal domains are similar to 3-ketoacyl-CoA thiolase and identical to the precursor of sterol carrier protein 2 (SCP2; also termed non-specific lipid-transfer protein), respectively. P-44 has 56(null)equence identity to the thiolase domain of SCx but lacks the SCP2 sequence. Northern blot analysis revealed only a single mRNA species of 1.4 kb, which agrees well with the length of the cDNA (1371 bp), making it improbable that alternative splicing produces an SCPx-like fusion protein. The sequence similarities of P-44 to conventional thiolases are lesser than that to SCPx. Purified recombinant P-44 cleaved long-chain 3-ketoacyl-CoAs (C8-16) in a thiolytic manner by the ping-pong bi-bi reaction mechanism. The inhibition of P-44 by acetyl-CoA was competitive with CoA and non-competitive with 3-ketooctanoyl-CoA. This pattern of inhibition is shared with SCPx but not with conventional 3-ketoacyl-CoA thiolase, which is inhibited uncompetitively with respect to 3-ketoacyl CoA. From these results, we concluded that nematode P-44 and mammalian SCPx constitute a second isoform of thiolase, which we propose to term type-II 3-ketoacyl-CoA thiolase.
Keywords
cDNA cloning
3-ketoacyl-CoA thiolase
sterol carrier protein x
sterol carrier protein 2
Caenorhabditis elegans
NDC
Biology [ 460 ]
Language
eng
Resource Type journal article
Publisher
Federation of European Biochemical Societies
Date of Issued 1997
Rights
Copyright (c) 1999 Federation of European Biochemical Societies
Publish Type Author’s Original
Access Rights open access
Source Identifier
[ISSN] 0014-2956
[NCID] AA00639541
[PMID] 9151950