The phytase RipBL1 enables the assignment of a specific inositol phosphate isomer as a structural component of human kidney stones

• Published in: RSC chemical biology Vol. 4; no. 4; pp. 3 - 39
• Main Authors: Liu, Guizhen, Riemer, Esther, Schneider, Robin, Cabuzu, Daniela, Bonny, Olivier, Wagner, Carsten A, Qiu, Danye, Saiardi, Adolfo, Strauss, Annett, Lahaye, Thomas, Schaaf, Gabriel, Knoll, Thomas, Jessen, Jan P, Jessen, Henning J
• Format: Journal Article
• Language: English
• Published: England RSC 05.04.2023
• Subjects: Chemistry
• ISSN: 2633-0679; 2633-0679
• DOI: 10.1039/d2cb00235c

Inositol phosphates (InsPs) are ubiquitous in all eukaryotes. However, since there are 63 possible different phosphate ester isomers, the analysis of InsPs is challenging. In particular, InsP 1 , InsP 2, and InsP 3 already amass 41 different isomers, of which some occur as enantiomers. Profiling of these "lower" inositol phosphates in mammalian tissues requires powerful analytical methods and reference compounds. Here, we report an analysis of InsP 2 and InsP 3 with capillary electrophoresis coupled to electrospray ionization mass spectrometry (CE-ESI-MS). Using this method, the bacterial effector RipBL1 was analyzed and found to degrade InsP 6 to Ins(1,2,3)P 3 , an understudied InsP 3 isomer. This new reference molecule then aided us in the assignment of the isomeric identity of an InsP 3 while profiling human samples: in urine and kidney stones, we describe for the first time the presence of defined and abundant InsP 3 isomers, namely Ins(1,2,3)P 3 , Ins(1,2,6)P 3 and/or Ins(2,3,4)P 3 . Kidney stones and patient urine contain inositol 1,2,3-trisphosphate as demonstrated by capillary electrophoresis mass spectrometry with an internal heavy isotope reference.