Comparative utilization of the alpha-keto and D- and L-alpha-hydroxy analogs of leucine, isoleucine and valine by chicks and rats.
Several experiments were conducted to quantitatively evaluate the growth-promoting capacity of the isomers of the branched-chain amino acids (BCAA) and their alpha-hydroxy and alpha-keto analogs for the chick and rat. Basal chemically defined diets were formulated to be singly deficient in the BCAA under study; analogs therefore were evaluated as sources of supplemental amino acid activity. DL-Isoleucine (DL-Ile), alpha-keto-beta-L-methylvaleric acid (KMV) and the isomers of alpha-hydroxy-beta-methylvaleric acid (HMV) were inferior to an isomolar level of L-Ile and varied considerably in their capacity to support growth of chicks and rats. Efficacy values of the compounds for chicks (C) and rats (R) were: DL-Ile 85% (C), 58% (R); KMV 60% (C), 38% (R); L-HMV 84% (C), 65% (R); DL-HMV 49% (C), 45% (R); and D-HMV -10% (C), -2% (R). The isomers of valine (Val) and alpha-hydroxyisovaleric acid (HIV) had efficacy values in chicks of: DL-Val, 84%; D-Val, 72%; L-HIV, 82%; DL-HIV, 79%; D-HIV, 66%. D-Val had only marginal growth-promoting activity for rats, 16%. All Val analogs had comparable efficacy values for the rat: alpha-ketoisovaleric acid (KIV), 49%; L-HIV, 54%; DL-HIV, 51%; and D-HIV, 46%. DL-Leu and D-Leu, alpha-ketoisocaproic acid (KIC), and L-, DL- and D-alpha-hydroxyisocaproic acid (HIC) were all less efficacious than isomolar amounts of supplemental L-Leu in rats. Efficacy values were: DL-Leu, 78%; D-Leu, 48%; KIC, 56%; L-HIC, 58%; DL-HIC, 55%; and D-HIC, 41%. The BCAA keto analogs were not superior to the L-alpha-hydroxy analogs in growth-promoting capacity, and this is of great interest for the potential use of these nitrogen-free amino acid analogs in nutritional therapy.
D000818:Animals; D002208:Caproates / Q000378:metabolism; D002645:Chickens; D045782:Hemiterpenes; D007532:Isoleucine / Q000031:analogs & derivatives* / Q000378:metabolism; D007651:Keto Acids / Q000378:metabolism; D007930:Leucine / Q000031:analogs & derivatives* / Q000378:metabolism; D008297:Male; D010421:Pentanoic Acids / Q000378:metabolism; D051381:Rats; D013045:Species Specificity; D013329:Structure-Activity Relationship; D014631:Valerates / Q000378:metabolism; D014633:Valine / Q000031:analogs & derivatives* / Q000378:metabolism
D002208:Caproates; D045782:Hemiterpenes; D007651:Keto Acids; D010421:Pentanoic Acids; D014631:Valerates; C035864:2-hydroxyisovaleric acid; D007532:Isoleucine; C016211:alpha-keto-beta-methylvaleric acid; C035865:2-hydroxy-3-methylvaleric acid; C019419:alpha-hydroxyisocaproic acid; C001505:alpha-ketoisovalerate; C013082:alpha-ketoisocaproic acid; D007930:Leucine; D014633:Valine