Morris James G
Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Nutr Res Rev. 2002 Jun;15(1):153-68. doi: 10.1079/NRR200238.
Cats have obligatory requirements for dietary nutrients that are not essential for other mammals. The present review relates these idiosyncratic nutritional requirements to activities of enzymes involved in the metabolic pathways of these nutrients. The high protein requirement of cats is a consequence of the lack of regulation of the aminotransferases of dispensable N metabolism and of the urea cycle enzymes. The dietary requirements for taurine and arginine are consequences of low activities of two enzymes in the pathways of synthesis that have a negative multiplicative effect on the rate of synthesis. Cats have obligatory dietary requirements for vitamin D and niacin which are the result of high activities of enzymes that catabolise precursors of these vitamins to other compounds. The dietary requirement for pre-formed vitamin A appears to result from deletion of enzymes required for cleavage and oxidation of carotenoids. The n-3 polyunsaturated fatty acids (PUFA) requirements have not been defined but low activities of desaturase enzymes indicate that cats may have a dietary need for pre-formed PUFA in addition to those needed by other animals to maintain normal plasma concentrations. The nutrient requirements of domestic cats support the thesis that their idiosyncratic requirements arose from evolutionary pressures arising from a rigorous diet of animal tissue. These pressures may have favoured energy conservation through deletion of redundant enzymes and modification of enzyme activities to result in metabolites more suited to the cat's metabolism. However, this retrospective viewpoint allows only recognition of association rather than cause and effect.
猫对某些膳食营养素有着必需的需求，而这些营养素对其他哺乳动物并非必需。本综述将这些独特的营养需求与参与这些营养素代谢途径的酶的活性联系起来。猫对蛋白质的高需求是由于非必需氮代谢的转氨酶和尿素循环酶缺乏调节所致。猫对牛磺酸和精氨酸的膳食需求是合成途径中两种酶活性较低的结果，这两种酶对合成速率具有负的倍增效应。猫对维生素D和烟酸有必需的膳食需求，这是由于将这些维生素的前体分解为其他化合物的酶活性较高所致。对预先形成的维生素A的膳食需求似乎是由于类胡萝卜素裂解和氧化所需的酶缺失所致。n-3多不饱和脂肪酸（PUFA）的需求尚未明确，但去饱和酶的低活性表明，除了其他动物维持正常血浆浓度所需的PUFA外，猫可能还需要预先形成的PUFA。家猫的营养需求支持了这样一种观点，即它们独特的需求源于以动物组织为严格饮食的进化压力。这些压力可能通过删除冗余酶和改变酶活性来促进能量守恒，从而产生更适合猫代谢的代谢物。然而，这种回顾性观点只能识别关联而非因果关系。
