Domestic cat urine contains large concentrations of the unusual amino acid, felinine (2-amino-7-hydroxy-5,5-dimethyl-4-thiaheptanoic acid). A felinine derivative, 3-mercapt-3-methylbutanol is a potential scent signal for letting other animals know that the scent owners are cats. 3-Methylbutanol-glutathione (MBG) is an upstream precursor of the biosynthetic pathway of felinine that may be produced in hepatocytes by conjugation of glutathione with isopentenyl pyrophosphate, an intermediate for cholesterol biosynthesis. However, little evidence exists to support the biosynthesis of MBG in the liver. This study examined the distribution of metabolites of the felinine biosynthetic pathway in multiple tissues, body fluids, and excretions of cats. MBG, the felinine precursor, 3-methylbutanol-cysteinylglycine (MBCG), felinine, and felinine N-acetyl derivative were quantified by liquid chromatography-electron spray ionization-tandem mass spectrometry. All compounds were detected in cat serum. In males, MBG and MBCG contents were significantly higher than felinine and N-acetylfelinine contents. MBG was detected in multiple tissues, including the salivary gland, heart, liver, spleen, gut, kidney, bladder, adipose tissue, and muscle. Sex differences in MBG levels were observed in the liver and other tissues. Felinine and N-acetylfelinine were also detected in those tissues. Furthermore, we detected all compounds in cat bile and fecal samples, indicating that felinine is excreted into the feces via bile from the liver. We conclude that MBG is synthesized in several tissues in a sex-dependent manner. These findings improve our understanding of felinine metabolism and function in cats.

家猫尿中含有高浓度的不常见氨基酸，猫氨酸（2-氨基-7-羟基-5,5-二甲基-4-硫庚庚酸）。一种猫精衍生物3-巯基-3-甲基丁醇是一种潜在的气味信号，可让其他动物知道该气味的主人是猫。3-甲基丁醇-谷胱甘肽（MBG）是丝氨酸生物合成途径的上游前体，可通过将谷胱甘肽与焦磷酸异戊烯酯（胆固醇生物合成的中间体）结合而在肝细胞中产生。但是，几乎没有证据支持肝脏中MBG的生物合成。这项研究检查了猫的生物合成途径中猫的多种组织，体液和排泄物中代谢产物的分布。MBG，猫碱前体，3-甲基丁醇-半胱氨酸甘氨酸（MBCG），猫碱和猫碱通过液相色谱-电子喷雾电离-串联质谱法对N-乙酰基衍生物进行定量。在猫血清中检测到所有化合物。在男性中，MBG和MBCG的含量显着高于女性蛋白和N-乙酰基女性蛋白的含量。在多种组织中检测到MBG，包括唾液腺，心脏，肝脏，脾脏，肠道，肾脏，膀胱，脂肪组织和肌肉。在肝脏和其他组织中观察到MBG水平存在性别差异。Felinine和N在这些组织中也检测到了-乙酰基丝氨酸。此外，我们在猫胆汁和粪便样品中检测到所有化合物，这表明猫氨酸通过胆汁从肝脏排泄到粪便中。我们得出结论，MBG是在几种组织中以性别依赖性方式合成的。这些发现提高了我们对猫中猫氨酸代谢和功能的了解。