Table 1 Main characteristic of HA synthases from Class I and II

Organisms

Streptococcus pyogenes, S. equisimilis, S. uberis, mammalian and avian

Amphibian species, algal virus

HAS of Pasteurella multocida

Size (amino acids)

417–588

972

Membrane attachment domain

6–8 membrane-associated domains

C-terminal membrane anchor

HA chain growth

At reducing end

At nonreducing end

At nonreducing end

Reaction type

Hexosyl group transfer

hexosyl group transfer

Metals and ions

Co²⁺; KCl; Mg²⁺; Mn²⁺; NaCl

Co²⁺; Mg²⁺; Mn²⁺;

K_M value [mM]

0.032–1.1

0.014-0.91

Ki value [mM]

1.2–4.5

ND

pH optimum

5–9

ND

Temperature optimum (ºC)

22–60

ND