Table 1.

Substrate specificity of 3Hyp sites in A-clade collagen α-chains.

Mammal (human)
Type	A4 Site	A3 Site	A2 Site	A1 Site
α1(I)	0%	0%	0%	99%
α2(I)	0%	80%	0%	n/a
α1(II)	0%	0%	10-87%	99%
α1(III)	n/a	0%	0%	0%
α2(V)	13%	80%	60%	99%
Avian (chicken)
Type	A4 Site	A3 Site	A2 Site	A1 Site
α1(I)	n/a	5-10%	0%	99%
α2(I)	n/a	95%	n/a	n/a
α1(II)	0%	18%	0%	99%
α1(III)	n/a	0%	0%	100%
α2(V)	18%	40%	28%	99%
Amphibian (xenopus)
Type	A4 Site	A3 Site	A2 Site	A1 Site
α1(I)	0%	12%	0%	99%
α2(I)	n/a	n/a	n/a	n/a
α1(II)	0%	n/a	0%	99%
α1(III)	n/a	0%	0%	100%

Molecular locations and abundance of 3Hyp sites within several vertebrates were identified using mass spectrometry. 3Hyp content was determined by scrolling the full scan to include all post-translational modification variations (n/a represents no substrate GPP in the known sequence). Note that only the A1 site is fully 3-hydroxylated across species.