{"doi":"10.1042/bj2100811","title":"The contribution of phenylalanine to tyrosine metabolism <i>in vivo</i>. Studies in the post-absorptive and phenylalanine-loaded rat","abstract":"<jats:p>1. Rates of appearance and oxidation of plasma L-leucine, L-phenylalanine and L-tyrosine, as well as conversion of plasma phenylalanine into plasma tyrosine, were determined in 90-120 g rats after overnight starvation and while receiving 115-120 mumol of L-phenylalanine/h. 2. In the post-absorptive state, plasma tyrosine and phenylalanine appearances were similar, despite the fact that 22% of plasma tyrosine appearance could be attributed to the hydroxylation of phenylalanine. 3. A constant infusion of 115-120 mumol of L-phenylalanine/h did not significantly alter plasma leucine kinetics, but increased appearance of plasma phenylalanine and tyrosine. The percentage of phenylalanine and tyrosine appearance that was oxidized increased from 12.1% and 24.4% to 37.3% and 48.0% respectively. In phenylalanine-loaded rats, 72% of plasma tyrosine appearance could be attributed to the conversion of phenylalanine. 4. Whole-body tyrosine oxidation measured from a continuous infusion of either L-[14C]tyrosine or L-[14C]phenylalanine differed by 165%. 5. It can be concluded that, in the post-absorptive state, phenylalanine hydroxylation makes a substantial contribution to the plasma appearance of tyrosine and is significantly increased when phenylalanine is administered. The disposal of excess infused phenylalanine is a result of a greater percentage of plasma phenylalanine being converted into tyrosine and a greater proportion of tyrosine being further oxidized. However, apparent tyrosine oxidation rates estimated from plasma tyrosine specific radioactivities and appearance of expired 14CO2 during administration of [14C]tyrosine are underestimates of true rates, in part because tyrosine generated from phenylalanine hydroxylation is catabolized without freely equilibrating with the plasma compartment.</jats:p>","journal":"Biochemical Journal","year":1983,"id":32217,"datarank":3.1382033467188277,"base_score":3.7376696182833684,"endowment":3.7376696182833684,"self_citation_contribution":0.5606504427425053,"citation_network_contribution":2.5775529039763225,"self_endowment_contribution":0.5606504427425053,"citer_contribution":2.5775529039763225,"corpus_percentile":null,"corpus_rank":null,"citation_count":41,"citer_count":34,"citers_with_citation_signal":34,"citers_with_endowment":34,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":170993,"name":"I Kawamura","orcid":null,"position":1,"is_corresponding":false},{"id":170994,"name":"B R Bistrian","orcid":null,"position":2,"is_corresponding":false},{"id":170995,"name":"G L Blackburn","orcid":null,"position":3,"is_corresponding":false},{"id":170992,"name":"L L Moldawer","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":3.7376696182833684,"endowment":3.7376696182833684,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"6870807","pmcid":"PMC1154294","openalex_id":"https://openalex.org/W2410579477","authors":[],"funders":[{"funder_name":"PHS HHS","grant_id":"24206","title":null},{"funder_name":"NIGMS NIH HHS","grant_id":"GM-22691","title":null},{"funder_name":"PHS HHS","grant_id":"24401","title":null}],"total_grants":3,"fwci":1.6551,"citation_percentile":0.83031272,"influential_citations":1,"citation_trend":[{"year":2013,"count":1},{"year":2017,"count":2},{"year":2019,"count":1},{"year":2023,"count":1}],"oa_status":"bronze","license":null,"oa_locations":[{"url":"https://portlandpress.com/biochemj/article-pdf/210/3/811/579311/bj2100811.pdf","host_type":"journal"},{"url":"https://europepmc.org/articles/pmc1154294?pdf=render","host_type":"GREEN"},{"url":"https://portlandpress.com/biochemj/article-pdf/210/3/811/579311/bj2100811.pdf","host_type":"publisher"},{"url":"https://doi.org/10.1042/bj2100811","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/6870807","host_type":"repository"},{"url":"https://www.ncbi.nlm.nih.gov/pmc/articles/1154294","host_type":"repository"}],"fields_of_study":["Biochemical Analysis and Sensing Techniques","Biochemical effects in animals","Metabolomics and Mass Spectrometry Studies","Chemistry","Medicine","Biology","Amino Acids","Animals","Kinetics","Leucine","Male","Oxidation-Reduction","Phenylalanine","Rats","Rats, Inbred Strains","Tyrosine"],"mesh_terms":["Amino Acids","Animals","Kinetics","Leucine","Male","Oxidation-Reduction","Phenylalanine","Rats, Inbred Strains","Tyrosine","Rats"],"keywords":["Phenylalanine","Tyrosine","Chemistry","Hydroxylation","Endocrinology","Leucine","Metabolism","Amino acid","Internal medicine","Biochemistry","Biology","Enzyme","Medicine"],"sdg_mappings":[{"sdg_number":0,"sdg_label":"Clean water and sanitation"}],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-09T10:53:02.493738Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}