Diphosphoinositol polyphosphates: metabolic messengers?
- Stephen B Shears
- Molecular pharmacology
The IUPAC Commissions on the Nomenclature of Inorganic and of Organic Chemistry (CNIC and CNOC) have recently provided, in the "D-Rules" (1), recommendations for naming a large number of organic compounds containing phosphorus. Many such compounds are extremely important in biochemistry and hence in nearly all branches of biology and medicine. Most of the biochemically important ones are esters and/or anhydrides of various phosphorus-containing acids with complex organic alcohols and organic acids. Strict application of the "D Rules" (1) to such compounds would result, in many cases, in rather complicated names, and these would be inconvenient for most biochemists and biologists to use. However, other systems of nomenclature, in use in the biochemical literature, are available (2-5). It is the purpose of this document to define and recommend certain of these for naming organic phosphorus-containing compounds in biochemical, biological, and medical publications. A general summary and explanation of the principles involved in the nomenclature of bioehemically important organic phosphorus compounds is given below. Representative compounds and their recommended names, together with those derived from more systematic nomenclature (4, 6, 7), including names formed according to the "D Rules" (1) where appropriate, are listed in the tables. 1. Phosphoric esters, RO-PO(OH)2, are named as O-substituted phosphorie acids or as substituted alcohols (Table 1). Thus, choline O-(dihydrogen phosphate) and O-phosphonocholine are both appropriate names. The latter may be contracted to phosphoeholine, but not changed to phosphorylcholine; "phosphoryl" is defined (ref. l, Rule 5.66) as OP~ and requires, if used, the naming of all three groups attached to the phosphorus atom. However, "phosphoryl" is retained in derived terms such as the names of enzymes (e.g., phosphorylase) or of processes (e.g., phosphorylation). Comment . The form O-phosphono-R stems from two considerations, (i) the definition (ref. 1, Rule 5.51) of phosphonic acid as HPO(OH)2, and (ii) the principle in organic nomenclature of substitution of another atom or group for a hydrogen atom of a parent molecule, which, in this case, involves the replacement of the H of an OH group by -P(O)(OH)z, the phosphono group (ref. 1, Rule 5.52).