Acyl-coenzyme A oxidases 1 (ACOX1) is the first rate-limiting enzyme responsible for peroxisomal β-oxidation. In the present study, two mRNA variants, ACOX1a and ACOX1b, transcribed from a single gene, were for the first time isolated and characterized from grass carp Ctenopharyngodon idella, both encoding putative peptides of 660 amino acids. Analysis of the exon-intron structures clarified that grass carp ACOX1a and ACOX1b comprise 14 coding exons and correspond to 3a and 3b isoforms of exon 3 splicing variants. Both ACOX1a and ACOX1b mRNAs were expressed in a wide range of tissues, but the abundance of each ACOX1 mRNA showed the tissue-dependent expression patterns. Time-course analysis of ACOX1 expressions indicated that the level of ACOX1a mRNA reached an almost maximal level at day 2, while that of ACOX1b mRNA reached an almost maximal level at day 8 during grass carp primary preadipocyte differentiation. In fasting-induced adipocyte lipolysis, only ACOX1a showed a significant increase in adipocyte, indicating that two ACOX1 isoforms may serve somewhat different roles in the peroxisomal β-oxidation. These results suggested that grass carp ACOX1a and ACOX1b were differently modulated by fasting in adipocyte. In addition, we found that mitochondrial β-oxidation might dominate at the early stage of fasting in adipocytes, indicating that mitochondria and peroxisomes might possess different capacities in fasting-induced adipocytes fatty acid oxidation.

酰基辅酶A氧化酶1（ACOX1）是负责过氧化物酶体β-氧化的第一个限速酶。在本研究中，首次从草鱼Ctenopharyngodon idella中分离并鉴定了从单个基因转录的两个mRNA变体ACOX1a和ACOX1b。，均编码660个氨基酸的推定肽。对外显子-内含子结构的分析表明，草鱼ACOX1a和ACOX1b包含14个编码外显子，分别对应于外显子3剪接变体的3a和3b亚型。ACOX1a和ACOX1b mRNA均在广泛的组织中表达，但每种ACOX1 mRNA的丰度均显示出组织依赖性的表达模式。ACOX1表达的时程分析表明，在草鱼原代前脂肪细胞分化过程中，ACOX1a mRNA的水平在第2天达到几乎最大水平，而ACOX1b mRNA的水平在第8天达到几乎最大水平。在空腹诱导的脂肪细胞脂解中，只有ACOX1a的脂肪细胞显着增加，这表明两种ACOX1亚型在过氧化物酶体β-氧化中可能起着不同的作用。这些结果表明，禁食脂肪细胞对草鱼ACOX1a和ACOX1b的调节不同。此外，我们发现线粒体β-氧化作用可能在禁食的脂肪细胞的早期占主导地位，这表明线粒体和过氧化物酶体在禁食诱导的脂肪细胞脂肪酸氧化中可能具有不同的能力。