Distribution of free amino acids, creatine, and trimethylamine oxide in mackerel and yellowtail.

The contents of free amino acids, creatine, and trimethylamine oxide (TMAO) in some tissues of mackerel Scomber japonicus and yellowtail Seriola quinqueradiata were determined and compared. The levels of creatine and TMAO in the dark muscle were relatively high. Creatine and histidine were present in extremely large amounts in the white muscle. The heart was com-paratively rich in creating, while in the liver, the levels of glutamic acid and alanine were high. The spleen had very low levels of all compounds determined. The level of nonprotein nitrogen was highest in the white muscle, followed by the dark muscle and the heart, and lowest was in either the liver or the spleen. Similarities in pattern of the distribution of these compounds were computed on the basis of these data and data of taurine reported previously. It was indicated that the pattern for the white muscle differs greatly from those for the dark muscle and the internal organs.