Novel extracellular enzymes (ligninases) of Phanerochaete chrysosporium

Abstract 3 New spectrophotometric enzyme assays were developed for the study of microbial lignin-degrading enzymes. The conversion of 2-methoxy-3-phenylbenzoic acid to 2-hydroxy-3-phenylbenzoic acid led to the discovery of an extracellular, aromatic methyl ether demethylase produced by the white-rot fungus Phanerochaete chrysosporium . The conversion of methyl 2-hydroxy-3-phenylbenzoate to 2-hydroxy-3-phenylbenzoic acid allowed the identification of an extracellular, aromatic methyl ester esterase produced by this fungus. The Phanerochaete sp. also excreted an enzyme complex that oxidized 4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one, probably to aliphatic products. All 3 novel enzyme activities were produced together with, and probably comprise a part of, the Phanerochaete ligninolytic enzyme complex. Unlike previously known ligninases, these enzymes did not oxidize 3,4-dimethoxybenzyl alcohol. All 3 were H₂O₂-dependent and were activated by Mn²⁺ ions.     

Calcium reduces the sodium permeability of luminal membrane vesicles from toad bladder. Studies using a fast-reaction apparatus

Regulation of the sodium permeability of the luminal membrane is the major mechanism by which the net rate of sodium transport across tight epithelia is varied. Previous evidence has suggested that the permeability of the luminal membrane might be regulated by changes in intracellular sodium or calcium activities. To test this directly, we isolated a fraction of the plasma membrane from the toad urinary bladder, which contains a fast, amiloride-sensitive sodium flux with characteristics similar to those of the native luminal membrane. Using a flow-quench apparatus to measure the initial rate of sodium efflux from these vesicles in the millisecond time range, we have demonstrated that the isotope exchange permeability of these vesicles is very sensitive to calcium. Calcium reduces the sodium permeability, and the half-maximal inhibitory concentration is 0.5 microM, well within the range of calcium activity found in cells. Also, the permeability of the luminal membrane vesicles is little affected by the ambient sodium concentration. These results, when taken together with studies on whole tissue, suggest that cell calcium may be an important regulator of transepithelial sodium transport by its effect on luminal sodium permeability. The effect of cell sodium on permeability may be mediated by calcium rather than by sodium itself.     

The effects of substrates on the optical rotatory dispersion of carnitine acetyltransferase

1. The optical rotatory dispersion of carnitine acetyltransferase is altered in the presence of l-carnitine or acetyl-l-carnitine. These changes, which include an increase in the reduced mean residue rotation at 233nm. ([M'](233)), suggest that substrate binding causes the enzyme to unfold. 2. CoA and acetyl-CoA have no immediate effect on [M'](233) and CoA has no effect on the change in this parameter induced by l-carnitine. 3. The change in [M'](233) was used as a measure of the degree of saturation of the enzyme with carnitine substrates. Dissociation constants for the enzyme complexes with l-carnitine, d-carnitine and acetyl-l-carnitine were determined in this way. 4. Prolonged incubation of carnitine acetyltransferase in the presence of CoA leads to a small increase in the value of [M'](233) accompanied by irreversible inhibition of the enzyme. 5. Optical-rotatory-dispersion studies of two specifically inhibited enzyme forms are reported.     

The biodegradation of piperazine and structurally-related linear and cyclic amines

The biodegradability of a range of linear and cyclic amines was assessed. All proved to be biodegradable but there were interesting differences in their susceptibility. The least degradable was piperazine although piperazine-degrading microorganisms were of widespread occurrence in samples of water and activated sludge and, to a lesser extent, soils. Piperazine degraders are only present in very small numbers — on averageca. 0.8/ml of river water. Of six isolates capable of using piperazine as a sole source of carbon, nitrogen and energy in pure culture five were identified asMycobacterium spp. and one asArthrobacter sp., all strains were capable only of slow growth (mean generation time ofca. 30 to 40 hours) on this substrate. Piperidine, pyrrolidine, ethanolamine and diethanolamine were all readily biodegradable. The relationship between structure and degradability of amines is discussed as are the possible reasons for the relative recalcitrance of piperazine.     

The influence of religious affiliation on surname repetition in marriages in Tiszaszalka, Hungary.

The repeated-pairs of surnames in marriages (RP) approach is applied to the population of Tiszaszalka in north-eastern Hungary. The results indicate that: (1) lineage-like behaviour in mate choice results in population subdivision in both the Catholics and the Protestants of the village; (2) unlike in some other Tiszahat villages, the isonymous and the repeating unions in Tiszaszalka occur in different lineages so, in neither of these subpopulations are isonymous and repeating unions monopolised by a few lineages; (3) religious affilitation influences the mating structure of the population as measured by RP summary scores.