Fatty acid compound containing one acyl group having from 6 to 12 carbon atoms, and preferably comprises, as an active ingredient, a fatty acid precursor that is converted to a fatty acid having 6 to 12 carbon atoms or in vivo fatty acid having 6 to 12 carbon atoms , degradation inhibitor of protein in vivo.炭素数6~12のアシル基を一つ含有する脂肪酸系化合物、好ましくは、炭素数6~12の脂肪酸または生体内で炭素数6~12の脂肪酸に変換される脂肪酸前駆体を有効成分として含む、生体内の蛋白質の分解抑制剤。