Plant Nucleotide Metabolism. Hiroshi Ashihara

such as nicotinamide mononucleotide (NMN), are called nucleotides only by extension and analogy, and nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are referred to as dinucleotides. Flavin mononucleotide (FMN) is a step further removed, as it contains ribitol, a pentose alcohol formed by the reduction of ribose, instead of ribose, while flavin adenine dinucleotide (FAD) similarly extends the meaning of dinucleotide. N-Glycosides such as orotidine 5′-monophosphate (OMP) and adenylosuccinate (SAMP) are called nucleotides through their close relationship to the ‘true’ nucleotides. The terms ribonucleoside and ribonucleotide are used in preference to riboside and ribotides. The IUPAC-IUB Combined Commission on Biochemical Nomenclature has abbreviations and symbols for nucleotides and related compounds. However, as argued by Henderson and Paterson (1973), while they are appropriate for polynucleotides, the distinction between bases and nucleosides is not always immediately obvious, and this has limited their use. The abbreviations used here are more intuitive and better suited to the portrayal of reaction schemes in which the addition or removal of substituent groups occurs.

In Table 1.1, the abbreviations for the major nucleotides, ribo- and deoxyribonucleotides and nucleobases are presented. For readers convenience, the styles used both in this book (style #1) and those recommended by IUPAC (style #2) are shown.

Table 1.1 Nomenclature and abbreviations of purine and pyridine ribo- and deoxyribonucleotides and related compounds.

Ribonucleotides		Ribonucleosides	#1	#2	Nucleobases	#1	#2
Adenosine-5′-monophosphate	AMP	Adenosine	AR	Ado	Adenine	A	Ade
Guanosine-5′-monophosphate	GMP	Guanosine	GR	Guo	Guanine	G	Gua
Inosine-5′-monophosphate	IMP	Inosine	IR	Ino	Hypoxanthine	H	Hyp
Xanthosine-5′-monophosphate	XMP	Xanthosine	XR	Xao	Xanthine	X	Xan
Uridine-5′-monophosphate	UMP	Uridine	UR	Urd	Uracil	U	Ura
Cytidine-5′-monophosphate	CMP	Cytidine	CR	Cyd	Cytosine	C	Cyt
Orotidine-5′-monophosphate	OMP	Orotidine	OR	Ord	Orotic acid	O	Oro
Deoxyribonucleotides		Deoxyribonucleosides	#1	#2	Nucleobases	#1	#2
Deoxyadenosine-5′-monophosphate	dAMP	Deoxyadenosine	AdR	dAdo	Adenine	A	Ade
Deoxyguanosine-5′-monophosphate	dGMP	Deoxyguanosine	GdR	dGuo	Guanine	G	Gua
Deoxyuridine-5′-monophosphate	dUMP	Deoxyuridine	UdR	dUrd	Uracil	U	Ura
Deoxycytidine-5′-monophosphate	dCMP	Deoxycytidine	CdR	dCyd	Cytosine	C	Cyt
Thymidine-5′-monophosphate	dTMP	Thymidine	TdR	dThd	Thymine	T	Thy

      Two types of symbols are used for nucleoside and nucleobases. Style #1: recommended in Nucleotide Metabolism (Henderson and Paterson 1973). Style #2: recommended by the IUPAC-IUB Commission on Biochemical Nomenclature (1970). In this book, style #1 is adopted.

      Abbreviations for ribonucleosides and 2-deoxyribonucleosides are derived from those used for the bases plus those for the ribosyl or 2′-deoxyribosyl groups. Thus AR stands for adenosine and AdR is the abbreviation for deoxyadenosine. In the case of inosine, (hypoxanthine + ribose) HR may be possible, but IR is often used. The latter is used in this text.

For nucleotides, the traditional abbreviations based on the term ‘nucleoside monophosphate’ are used. Thus AMP stands for adenosine monophosphate (adenylate), UMP for uridine monophosphate (uridylate), and NMP for any ribonucleoside monophosphate. Similarly, dAMP stands for deoxyadenosine monophosphate (deoxyadenylate), dUMP for deoxyuridine monophosphate (deoxyuridylate), and dNMP for any deoxyribonucleoside monophosphate. Thymidine monophosphate (thymidylate) often does not have the ‘deoxy’ prefix in its name, because thymidine is thymine deoxyriboside. However, the symbol including