Targeted mass spectrometry studies of plpbp−/− zebrafish larvae indicates changes in B6 vitamer, amino acid, and neurotransmitter profiles. (A) B6 vitamer profile of mutant and wild-type 10 dpf larvae. (B) Amino acid and neurotransmitter profile of whole larval mutant, heterozygous and wild-type 11 dpf larvae after 24 h fasting. (C) Metabolic pathways for the synthesis and degradation of PLP. (D) Biosynthetic pathways of catecholamines and trace amines, highlighting (in blue) the role of AADC. (E) The serotonin biosynthesis pathway, highlighting the role of AADC. 3-MT = 3-methoxytyramine; 5-HIAA = 5-hydroxyindoleacetic acid; 5-HTTP = 5-hydroxytrytpophan; AADC = aromatic-l-amino acid decarboxylase; AO = aldehyde oxidase I; DH = β-NAD dehydrogenase; PA = 4-pyridoxic acid; PK = pyridoxal kinase; PL = pyridoxal; PM = pyridoxamine; PMP = pyridoxamine 5′-phosphate; PN = pyridoxine; PNPO = PNP oxidase. Significance: ****P < 0.0001, ***P < 0.001, **P < 0.01, *P < 0.05.