P1PK: a blood group system with an identity crisis

Abstract

The P1PK blood group system (ISBT no. 003) was previously called the P blood group system, and the number of included antigens has varied over time. The history of the system is complicated and sometimes confusing, since several changes to the nomenclature have been made. Furthermore, the association between the antigens and their genetic home has raised many questions, as well as the long-standing enigma regarding the molecular mechanism underlying the common P 1 and P 2 phenotypes. Step by step, the biochemical and genetic basis underlying the antigens expressed in this system has been revealed. This review will start with the historical background and continue with the latest findings, answering some of the questions such as why individuals with p phenotype lack not only P k and P expression, but also P1, and whether the P1 antigens exist on both glycolipids and glycoproteins on the human red blood cells.

Human Gb3/CD77 synthase produces P1 glycotope-capped N-glycans, which mediate Shiga toxin 1 but not Shiga toxin 2 cell entry

“…The P1PK histo-blood group system continues to perplex. The conundrum of its genetic and biochemical background was covered in depth in reviews and original reports by us and other groups ( 4 , 32 , 33 , 34 , 35 ). One view that remained largely unchallenged for over 20 years was that the human Gb3/CD77 synthase (α1,4-galactosyltransferase, P1/P k synthase; EC 2.4.1.228) could only use GSLs as acceptors to produce Galα1→4Gal-terminated glycans (Gb3 and P1).…”

A novel P1PK allele in two Bangladeshi sisters with a history of spontaneous abortion: A4GALT*02N(951C)

“…The antigens of the P1PK system are synthesized by an α1,4‐galactosyltransferase (P1P k synthase) encoded by the A4GALT gene located on chromosome 22. The enzyme synthesizes the P1 antigen on paragloboside and the P k antigen on lactosylceramide 1 . Transcription regulation determines the main phenotypes, P 1 and P 2 , correlated with single nucleotide polymorphisms in non‐coding regions of A4GALT, particularly rs5751348 2,3 …”