Purification and characterization of a mesohalic catalase from the halophilic bacterium Halobacterium halobium

Abstract

When subjected to the stress of growth in a relatively low-salt environment (1.25 M NaCl), the halophilic bacterium Halobacterium halobium induces a catalase. The protein has been purified to electrophoretic homogeneity and has an M(r) of 240,000 and a subunit size of approximately 62,000. The enzyme is active over a broad pH range of 6.5 to 10.0, with a peak in activity at pH 7.0. It has an isoelectric point of 4.0. This catalse, which is not readily reduced by dithionite, shows a Soret peak at 406 nm. Cyanide and azide inhibit the enzyme at micromolar concentrations, whereas maleimide is without effect. The addition of 20 mM 3-amino-1,2,4-triazole results in a 33% inhibition in enzymatic activity. The tetrameric protein binds NADP in a 1:1 ratio but does not peroxidize NADPH, NADH, or ascorbate. Although the enzymatic activity is maximal when assayed in a 50 mM potassium phosphate buffer with no NaCl, prolonged incubation in a buffer lacking NaCl results in inactive enzyme. Moreover, purification must be performed in the presence of 2 M NaCl. Equally as effective in retaining enzymatic function are NaCl, LiCl, KCl, CsCl, and NH4Cl, whereas divalent salts such as MgCl2 and CaCl2 result in the immediate loss of activity. The catalase is stained by pararosaniline, which is indicative of a glycosidic linkage. The Km for H2O2 is 60 mM, with inhibition observed at concentrations in excess of 90 mM. Thus, the mesohalic catalase purified from H. halobium seems to be similar to other catalases, except for the salt requirements, but differs markedly from the constitutive halobacterial hydroperoxidase.

Purification and Characterization of a Catalase from the Facultatively Psychrophilic Bacterium Vibrio rumoiensis S-1 T Exhibiting High Catalase Activity

“…To date, there have been several reports of unique catalases from halophiles (5,6,12), thermophiles (27,41), and alkaliphiles (16,42). However, there have been no reports of psychrophilic catalases isolated from psychrophilic microorganisms.…”

“…The mammal type catalases are commonly isolated from animals, plants, fungi, and bacteria, and their molecular features are similar to each other: they are composed of four subunits of equal size containing 2.5 to 4 protohemes IX per tetramer, with a molecular mass range of 225 to 270 kDa. They exhibit a broad optimum pH range of 5 to 10, are resistant to treatment with organic solvents, are glycoproteins, and are inhibited by 3-amino-1,2,4-triazole (6,8,22,33,38). The catalase-peroxidases, which are isolated from bacteria and fungi, have several properties that distinguish them from the typical catalases: they are reduced by dithionite, they are not glycoproteins, their activity is pH dependent, and they are more sensitive to heat, organic solvents, and H 2 O 2 than the typical catalases, but they are insensitive to 3-amino-1,2,4-triazole (5,11,18,29,33,42).…”

Unique Presence of a Manganese Catalase in a Hyperthermophilic Archaeon, Pyrobaculum calidifontis VA1

“…(11,12,14,41,42), but there have been no previous reports of a manganese catalase. Recently, an abundant number of complete genome sequences from various archaeal strains have been determined.…”

“…A catalase-peroxidase and a monofunctional catalase were purified from the halophilic archaeon Halobacterium halobium (11,12), and a catalase-peroxidase was also purified…”

“…A catalase-peroxidase and a monofunctional catalase were purified from the halophilic archaeon Halobacterium halobium (11,12), and a catalase-peroxidase was also purified from Haloarcula marismortui (14). In methanogenic archaea, monofunctional catalases were purified from Methanosarcina barkeri (41) and Methanobrevibacter arboriphilus (42).…”