Terrestrial enzymes

It has been pointed out previously [49] that many terrestrial enzymes can still be active in non-polar solvents such as ethers and benzene and that about 20% of the human genome encodes trans-membrane proteins that require the nrai-polar environments inside membranes to operate. Although these observatiOTis do not provide any direct evidence for the possibility of non-aqueous solvents being potentially successful media for biochemistry, they show that even terrestrial biochemistiy can operate in non-aqueous solvents and in the case of trans-membrane proteins, actually require these environments. 

Starch A polymeric substance of glucose molecules and a component of many terrestrial and aquatic plants used by some organisms as a means of energy storage starch is broken down by enzymes (amylases) to yield glucose, which can be used as a feedstock for chemical or energy production. 

All sea snakes are poisonous and their venoms are extremely toxic. The LD q for crude sea snake venom can be as low as 0.10 fig/g mouse body weight (i). For purified toxin the LD q is even lower, suggesting the high toxicity of sea snake toxins and venoms. This toxicity is derived from the presence of potent neurotoxins. Compared to snake venoms of terrestrial origin, sea snake venoms have been studied less. Different enzymes reported to be present or absent are summarized in Table I. 

Some haloperoxidases contain vanadium and a review of vanadium peroxidases has been given (Butler 1998). The structure of the vanadium enzyme in the terrestrial fungus Cur-vularia inaequalis has been determined by x-ray analysis (Messerschmidt et al. 1997), and the apochloroperoxidase possesses, in addition, phosphatase activity that can be rationalized on the basis of the isomorphism of phosphate and vanadate (Renirie et al. 2000). 

As already noted, MT has several sources such as lyase enzymes for L-methionine and S -methyl-L-cysteine. There are complex relationships between DMS, MT, and other VOSCs in the atmosphere, and in marine and terrestrial environments. The previously cited reviews should be consulted. 

Copper is part of several essential enzymes including tyrosinase (melanin production), dopamine beta-hydroxylase (catecholamine production), copper-zinc superoxide dismutase (free radical detoxification), and cytochrome oxidase and ceruloplasmin (iron conversion) (Aaseth and Norseth 1986). All terrestrial animals contain copper as a constituent of cytochrome c oxidase, monophenol oxidase, plasma monoamine oxidase, and copper protein complexes (Schroeder et al. 1966). Excess copper causes a variety of toxic effects, including altered permeability of cellular membranes. The primary target for free cupric ions in the cellular membranes are thiol groups that reduce cupric (Cu+2) to cuprous (Cu+1) upon simultaneous oxidation to disulfides in the membrane. Cuprous ions are reoxidized to Cu+2 in the presence of molecular oxygen molecular oxygen is thereby converted to the toxic superoxide radical O2, which induces lipoperoxidation (Aaseth and Norseth 1986). 

Goven, A.J., S.C. Chen, L.C. Fitzpatrick, and B.J. Venables. 1994. Lysozyme activity in earthworm (Lumbricus terrestris) coelomic fluid and coelomocytes enzyme assay for immunotoxicity of xenobiotics. Environ. Toxicol. Chem. 13 607-613. 

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