Table II.

Substrate specificity of PPD types 1 and 2 from cotyledons of radish

The C-position number refers to the structure formula of Pheid a in Figure 1. Preparation of Chl derivatives and the enzyme assay were performed as described in the text.

Chl Species	Metal (Mg)	C-Position				Km
		C17a	C7	C17-C18b	C7-C8b	Type 1	Type 2
						μm
Porphyrins
ProtoChlid a	+	Propionyl	CH3	Double	Double	–	–
ProtoPheid a	−	Propionyl	CH3	Double	Double	–	–
Pheophytin c	−	Acryl	CH3	Double	Double	–	–
Dihydroporphyrins
Chl a	+	Phytyl	CH3	Single	Double	–	–
Chl b	+	Phytyl	CHO	Single	Double	–	–
Chlid a	+	Propionyl	CH3	Single	Double	–	–
Pheophytin a	−	Phytyl	CH3	Single	Double	–	–
Pheid a	−	Propionyl	CH3	Single	Double	14	15
Pheid a′	−	Propionyl	CH3	Single	Double	–	–
Pheid b	−	Propionyl	CHO	Single	Double	243	232
Tetrahydroporphyrins
Bacterio-Chl a	+	Phytyl	CH3	Single	Single	–	–
Bacterio-Pheid a	−	Propionyl	CH3	Single	Single	39	37

^aPhytyl, -CH₂-CH₂-COOC₂₀H₃₀; propionyl, -CH₂-CH₂-COOH; acryl, -CH = CH-COOH.

^bSingle, single bond; Double, double bond.