= Adenylyl group
An \b[adenylyl group] is the <adenosine monophosphate>-derived portion transferred in an adenylyl-transfer reaction. It includes the <adenosine> unit and one phosphorus-containing group; it is not simply <adenine> detached from its <ribose>. The IUBMB recommends \i[adenylyl], rather than \i[adenyl], for nucleotide groups.<Enzyme Nomenclature by the IUBMB>[Rules and Guidelines, nucleotide-group naming recommendation: adenylyl rather than adenyl.]{ref}
A concrete example is <FAD synthase>, whose systematic name is ATP:FMN adenylyltransferase. It transfers an <ATP>-derived adenylyl portion to <flavin mononucleotide>, forming <flavin adenine dinucleotide> and releasing <diphosphate>:
$$
\mathrm{ATP}+\mathrm{FMN}\longrightarrow\mathrm{FAD}+\mathrm{PP_i}.
$$
The reaction identifies which part of <ATP> is incorporated, rather than merely recording ATP consumption.<Enzyme Nomenclature by the IUBMB>[EC 2.7.7.2, Reaction and Systematic name.]{ref}
An original bookkeeping example makes the distinction visible. Complete conversion of 10 nmol of <flavin mononucleotide> using 20 nmol of <ATP>, with no side reactions, gives 10 nmol each of <flavin adenine dinucleotide> and <diphosphate>, leaving 10 nmol of <ATP>. The initial phosphorus inventory is $3(20)+1(10)=70$ nmol of phosphorus atoms; the final inventory is $2(10)+2(10)+3(10)=70$. Conservation checks the accounting but cannot, by itself, identify the products.
Back to article page
