Table 1.

Biochemical characteristics of purified SHCs^a

Species	Molecular mass (kDa)	pH/temperature optimum (°C)	2,3-Oxidosqualene cyclization	Tetrahymanol formation	Remark	Reference(s)
Alicyclobacillus acidocaldarius	71.6	6/60	Yes	No	Km of ∼3-16 μM	16, 38, 56, 57, 86, 87
Bradyrhizobium japonicum	76.3	6.5/28	Yes	No		43, 57, 68, 69
Methylococcus capsulatus	74.1	6.8/40	No	No		78, 95
Rhodopseudomonas palustris	72.3	6.5/30	–	No	Active between pH 5 and pH 8	44
Streptomyces peucetius	74.1	6.8/35	–	–		29
Tetrahymena thermophila	72*	7.0/30	–	Yes	Km of ∼18 μM	80
Zymomonas mobilis	74.1	6.0/30	–	–		77

^aThe molecular masses were calculated based on the amino acid sequence if not otherwise indicated. 2,3-Oxidosqualene and tetrahymanol were analyzed as substrate/product, respectively. Cyclization of squalene is catalyzed by all SHCs (not included in table). –, substrate/product was not investigated; *, estimated from SDS-PAGE.