{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,21]],"date-time":"2026-03-21T16:51:57Z","timestamp":1774111917794,"version":"3.50.1"},"reference-count":27,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2023,11,10]],"date-time":"2023-11-10T00:00:00Z","timestamp":1699574400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002428","name":"Austrian Science Fund FWF","doi-asserted-by":"publisher","award":["I4695-B"],"award-info":[{"award-number":["I4695-B"]}],"id":[{"id":"10.13039\/501100002428","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002428","name":"Austrian Science Fund FWF","doi-asserted-by":"publisher","award":["I4704-B"],"award-info":[{"award-number":["I4704-B"]}],"id":[{"id":"10.13039\/501100002428","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Paracelsus Medical University","award":["I4695-B"],"award-info":[{"award-number":["I4695-B"]}]},{"name":"Paracelsus Medical University","award":["I4704-B"],"award-info":[{"award-number":["I4704-B"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Metabolites"],"abstract":"<jats:p>Two siblings showed increased galactose and galactose-related metabolites in neonatal screening. Diagnostic workup did not reveal abnormalities in any of the known disease-causing enzymes involved in galactose metabolism. Using whole-exome sequencing, we identified a homozygous missense variant in PPA1 encoding the cytosolic pyrophosphatase 1 (PPA1), c.557C&gt;T (p.Thr186Ile). The enzyme activity of PPA1 was determined using a colorimetric assay, and the protein content was visualized via western blotting in skin fibroblasts from one of the affected individuals. The galactolytic activity of the affected fibroblasts was determined by measuring extracellular acidification with a Seahorse XFe96 analyzer. PPA1 activity decreased to 22% of that of controls in the cytosolic fraction of homogenates from patient fibroblasts. PPA1 protein content decreased by 50% according to western blot analysis, indicating a reduced stability of the variant protein. The extracellular acidification rate was reduced in patient fibroblasts when galactose was used as a substrate. Untargeted metabolomics of blood samples revealed an elevation of other metabolites related to pyrophosphate metabolism. Besides hyperbilirubinemia in the neonatal period in one child, both children were clinically unremarkable at the ages of 3 and 14 years, respectively. We hypothesize that the observed metabolic derangement is a possible mild manifestation of PPA1 deficiency. Unresolved abnormalities in galactosemia screening might result in the identification of more individuals with PPA1 deficiency, a newly discovered inborn metabolic disorder (IMD).<\/jats:p>","DOI":"10.3390\/metabo13111141","type":"journal-article","created":{"date-parts":[[2023,11,10]],"date-time":"2023-11-10T05:04:56Z","timestamp":1699592696000},"page":"1141","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["PPA1 Deficiency Causes a Deranged Galactose Metabolism Recognizable in Neonatal Screening"],"prefix":"10.3390","volume":"13","author":[{"given":"Melanie T.","family":"Achleitner","sequence":"first","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0960-6263","authenticated-orcid":false,"given":"Judith J. M.","family":"Jans","sequence":"additional","affiliation":[{"name":"Department of Genetics, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands"},{"name":"Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Laura","family":"Ebner","sequence":"additional","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8519-1269","authenticated-orcid":false,"given":"Johannes","family":"Spenger","sequence":"additional","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vassiliki","family":"Konstantopoulou","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Austrian Newborn Screening, Medical University of Vienna, 1090 Vienna, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4215-8258","authenticated-orcid":false,"given":"Ren\u00e9 G.","family":"Feichtinger","sequence":"additional","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Karin","family":"Brugger","sequence":"additional","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Doris","family":"Mayr","sequence":"additional","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2278-9746","authenticated-orcid":false,"given":"Ron A.","family":"Wevers","sequence":"additional","affiliation":[{"name":"Department of Human Genetics, Translational Metabolic Laboratory, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6419-8747","authenticated-orcid":false,"given":"Christian","family":"Thiel","sequence":"additional","affiliation":[{"name":"Center for Child and Adolescent Medicine, Pediatrics I, University Heidelberg, Analysezentrum 3, 69120 Heidelberg, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1968-8103","authenticated-orcid":false,"given":"Saskia B.","family":"Wortmann","sequence":"additional","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"},{"name":"Amalia Children\u2019s Hospital, Radboudumc, 6525 GA Nijmegen, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6970-336X","authenticated-orcid":false,"given":"Johannes A.","family":"Mayr","sequence":"additional","affiliation":[{"name":"University Children\u2019s Hospital, Salzburger Landeskliniken (SALK), Paracelsus Medical University, 5020 Salzburg, Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,11,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1003","DOI":"10.1007\/s10545-015-9893-x","article-title":"Quo vadis: The re-definition of \u201cinborn metabolic diseases\u201d","volume":"38","author":"Morava","year":"2015","journal-title":"J. Inherit. Metab. Dis."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"317","DOI":"10.2471\/BLT.07.050112","article-title":"Revisiting Wilson and Jungner in the genomic age: A review of screening criteria over the past 40 years","volume":"86","author":"Andermann","year":"2008","journal-title":"Bull. World Health Organ."},{"key":"ref_3","first-page":"17.5.1","article-title":"Diagnosis of inherited disorders of galactose metabolism","volume":"56","author":"Cuthbert","year":"2008","journal-title":"Curr. Protoc. Hum. Genet."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"12168","DOI":"10.1016\/S0021-9258(18)98875-7","article-title":"Yeast PPA2 gene encodes a mitochondrial inorganic pyrophosphatase that is essential for mitochondrial function","volume":"266","author":"Lundin","year":"1991","journal-title":"J. Biol. Chem."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2415","DOI":"10.1038\/s41436-021-01296-6","article-title":"PPA2-associated sudden cardiac death: Extending the clinical and allelic spectrum in 20 new families","volume":"23","author":"Guimier","year":"2021","journal-title":"Genet. Med."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1012090","DOI":"10.3389\/fonc.2022.1012090","article-title":"PPA1, an energy metabolism initiator, plays an important role in the progression of malignant tumors","volume":"12","author":"Wang","year":"2022","journal-title":"Front. Oncol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1278","DOI":"10.2337\/db20-0622","article-title":"PPA1 Regulates Systemic Insulin Sensitivity by Maintaining Adipocyte Mitochondria Function as a Novel PPARgamma Target Gene","volume":"70","author":"Yin","year":"2021","journal-title":"Diabetes"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"607","DOI":"10.1007\/s00508-010-1457-3","article-title":"The national Austrian newborn screening program\u2014Eight years experience with mass spectrometry. past, present, and future goals","volume":"122","author":"Kasper","year":"2010","journal-title":"Wien. Klin. Wochenschr."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1399","DOI":"10.1542\/peds.111.6.1399","article-title":"Expanded newborn screening for inborn errors of metabolism by electrospray ionization-tandem mass spectrometry: Results, outcome, and implications","volume":"111","author":"Schulze","year":"2003","journal-title":"Pediatrics"},{"key":"ref_10","first-page":"811","article-title":"Investigation of Hereditary Cancer Predisposition Genes of Patients with Colorectal Cancer: Single-centre Experience","volume":"30","author":"Duzkale","year":"2021","journal-title":"J. Coll. Physicians Surg. Pak."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1046","DOI":"10.1038\/s41588-020-0695-1","article-title":"Mutations disrupting neuritogenesis genes confer risk for cerebral palsy","volume":"52","author":"Jin","year":"2020","journal-title":"Nat. Genet."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"354","DOI":"10.1111\/cge.13603","article-title":"Confirmation that variants in TTI2 are responsible for autosomal recessive intellectual disability","volume":"96","author":"Ziegler","year":"2019","journal-title":"Clin. Genet."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Haijes, H.A., Willemsen, M., Van der Ham, M., Gerrits, J., Pras-Raves, M.L., Prinsen, H., Van Hasselt, P.M., De Sain-van der Velden, M.G.M., Verhoeven-Duif, N.M., and Jans, J.J.M. (2019). Direct Infusion Based Metabolomics Identifies Metabolic Disease in Patients\u2019 Dried Blood Spots and Plasma. Metabolites, 9.","DOI":"10.3390\/metabo9010012"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"e14397","DOI":"10.15252\/emmm.202114397","article-title":"Characterising a homozygous two-exon deletion in UQCRH: Comparing human and mouse phenotypes","volume":"13","author":"Vidali","year":"2021","journal-title":"EMBO Mol. Med."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1147","DOI":"10.1017\/S0022215100098327","article-title":"Nasal tooth","volume":"99","author":"Spencer","year":"1985","journal-title":"J. Laryngol. Otol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1203\/00006450-198908000-00016","article-title":"Heterogeneity of defects in mitochondrial acetoacetyl-CoA thiolase biosynthesis in fibroblasts from four patients with 3-ketothiolase deficiency","volume":"26","author":"Nagasawa","year":"1989","journal-title":"Pediatr. Res."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"674","DOI":"10.1016\/j.ajhg.2016.06.027","article-title":"Sudden Cardiac Death Due to Deficiency of the Mitochondrial Inorganic Pyrophosphatase PPA2","volume":"99","author":"Kennedy","year":"2016","journal-title":"Am. J. Hum. Genet."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"5198","DOI":"10.1111\/febs.16413","article-title":"Mitochondrial and metabolic remodelling in human skin fibroblasts in response to glucose availability","volume":"289","author":"Pinho","year":"2022","journal-title":"FEBS J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1226","DOI":"10.1038\/gim.2017.41","article-title":"Oral D-galactose supplementation in PGM1-CDG","volume":"19","author":"Wong","year":"2017","journal-title":"Genet. Med."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"887","DOI":"10.1007\/s10545-012-9531-9","article-title":"Screening for congenital disorders of glycosylation in the first weeks of life","volume":"36","author":"Thiel","year":"2013","journal-title":"J. Inherit. Metab. Dis."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"274","DOI":"10.1016\/j.ymgme.2022.06.005","article-title":"Missense variant c.1460 T > C (p.L487P) enhances protein degradation of ER mannosyltransferase ALG9 in two new ALG9-CDG patients presenting with West syndrome and review of the literature","volume":"136","author":"Himmelreich","year":"2022","journal-title":"Mol. Genet. Metab."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"405","DOI":"10.1038\/gim.2015.30","article-title":"Standards and guidelines for the interpretation of sequence variants: A joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology","volume":"17","author":"Richards","year":"2015","journal-title":"Genet. Med."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1031","DOI":"10.1002\/humu.24291","article-title":"Utilizing ClinGen gene-disease validity and dosage sensitivity curations to inform variant classification","volume":"43","author":"Thaxton","year":"2022","journal-title":"Hum. Mutat."},{"key":"ref_24","unstructured":"Kalakonda, A., Jenkins, B.A., and John, S. (2023). StatPearls, StatPearls Publishing."},{"key":"ref_25","unstructured":"Barmore, W., Azad, F., and Stone, W.L. (2023). StatPearls, StatPearls Publishing."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1186\/1750-1172-7-32","article-title":"Suggested guidelines for the diagnosis and management of urea cycle disorders","volume":"7","author":"Haberle","year":"2012","journal-title":"Orphanet J. Rare Dis."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Durrant, C., Fuehring, J.I., Willemetz, A., Chretien, D., Sala, G., Ghidoni, R., Katz, A., Rotig, A., Thelestam, M., and Ermonval, M. (2020). Defects in Galactose Metabolism and Glycoconjugate Biosynthesis in a UDP-Glucose Pyrophosphorylase-Deficient Cell Line Are Reversed by Adding Galactose to the Growth Medium. Int. J. Mol. Sci., 21.","DOI":"10.3390\/ijms21062028"}],"container-title":["Metabolites"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2218-1989\/13\/11\/1141\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:20:58Z","timestamp":1760131258000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2218-1989\/13\/11\/1141"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,11,10]]},"references-count":27,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2023,11]]}},"alternative-id":["metabo13111141"],"URL":"https:\/\/doi.org\/10.3390\/metabo13111141","relation":{},"ISSN":["2218-1989"],"issn-type":[{"value":"2218-1989","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,11,10]]}}}