RELAXING EFFECTS OF FORMAMIDE ON GLYCERINATED MUSCLE FIBERS AND ON MYOSIN B SUSPENSION

Acetone induces a reversible relaxation of glycerinated muscle fibers (1). We found that formamide is equally effective. Since the dielectric constant of formamide is larger and that of acetone is smaller than that of water, the change in the dielectric constant of the fiber medium after adding organic solvents has little to do with the mechanism of this organic solvent-induced relaxation. That ITP can substitute for ATP in this relaxation suggests that organic solvents, when they induce a relaxation, act on the contractile protein rather than on ATP. Comparing the relaxing effect of 11 different organic solvents, the authors propose a working hypothesis based on the assumption of a specific interaction between organic solvents and the contractile protein. Formamide induces a "clearing" response of myosin B suspensions which is an in vitro model of muscle relaxation. Effects of Mg, Ca, and ionic strength (KCl) on this clearing response are studied in comparison with the effects of these on EDTA-induced relaxation. It is then shown that the formamide-induced clearing response is less specific than the EDTA-induced clearing response with regard to the requirements for ATP and Mg.

METHYL KETONE METABOLISM IN HYDROCARBON-UTILIZING MYCOBACTERIA

Lukins, H. B. (University of Texas, Austin) and J. W. Foster. Methyl ketone metabolism in hydrocarbon-utilizing mycobacteria. J. Bacteriol. 85: 1074-1087. 1963.-Species of Mycobacterium especially M. smegmatis 422, produced the homologous methyl ketones during the oxidation of propane, n-butane, n-pentane, or n-hexane. A carrier-trapping experiment demonstrated the formation of 2-undecanone, as well as 1,11-undecanedioic acid, during the oxidation of undecane-1-C(14). Aliphatic alkane-utilizing mycobacteria were able to grow at the expense of several aliphatic methyl ketones as sole sources of carbon. Other ketones which did not support growth were oxidized by resting bacterial suspensions. M. smegmatis 422 cells grown on propane or acetone were simultaneously adapted to oxidize both substrates, as well as n-propanol. n-Propanol cells were unadapted to propane or acetone. Acetone produced from propane in a medium enriched in D(2)O contained a negligible quantity of D, presumably eliminating propylene as an intermediate in the oxidation. Cells grown at the expense of alkanes or methyl ketones in the presence of O(2) (18) had a higher content of O(18) than did cells grown on terminally oxidized compounds, e.g., primary alcohols or fatty acids. An oxygenase reaction is postulated for the attack on methyl ketones. Acetol was isolated and characterized as an oxidation product of acetone by M. smegmatis 422. Acetol-grown cells had a higher O(18) content than did n-propanol cells, and its utilization appears to involve at least one oxygenase reaction. Acetol produced from acetone in the presence of O(2) (18) was not enriched in the isotope, indicating the occurrence of exchange reactions or of oxygenation reactions at a later stage in the assimilation of acetone and acetol.

PURIFICATION OF A SALT-REQUIRING ENZYME FROM AN OBLIGATELY HALOPHILIC BACTERIUM

Holmes, P. K. (University of Illinois, Urbana), and H. O. Halvorson. Purification of a salt-requiring enzyme from an obligately halophilic bacterium. J. Bacteriol. 90: 312-315. 1965.-The discovery that some halophilic enzymes may be reactivated from the salt-free and inactive state has facilitated the purification of nicotinamide adenine dinucleotide-linked malic acid dehydrogenase from crude extracts of Halobacterium salinarium. In the absence of large amounts of salt, the enzyme was totally inactive; yet, in this salt-free state, it could be purified by conventional techniques. The highly purified halophilic enzyme was shown to require a high concentration of salt for activity.

THE CYTOCHROMES OF ISOLATED CHLOROPLASTS

Suspensions of chloroplasts extracted from leaves of Vicia faba L. were purified to the extent that no cytoplasmic impurities were detectable in electron micrographs. These suspensions contained cytochrome b 6 and cytochrome f and none of the cytochromes found in mitochondria. Both cytochromes present were limited to the lamellae of the grana, i.e. to the same site as the chlorophylls. The molar ratios chlorophyll a :chlorophyll b :cytochrome b 6 :cytochrome f were estimated at about 460:260:2.5:1. It is suggested that the cytochromes, possibly a single molecule each of cytochrome b 6 and cytochrome f , may form the node around which the 'photosynthetic unit’ is organized.

URINARY AMINO-ACETONE EXCRETION IN LEAD WORKERS

Urinary amino-acetone concentrations were determined in a group of 51 persons with industrial exposure to lead and the findings compared with those obtained from a control group of 27 persons having no exposure to lead.A good correlation was found between delta-aminolaevulinic acid and amino-acetone excretion in the control group but this correlation was not so well defined in the lead-exposed group. In this group excretion of amino-acetone seemed to be better correlated with excretion of delta-aminolaevulinic acid for values less than 0.6 mg.% than with values greater than 0.6 mg.%. All the men concerned in the investigation were employed in dusty occupations. Hypotheses are put forward to attempt to explain the differences in excretion of amino-acetone noted amongst lead workers with high excretion of delta aminolaevulinic acid.Little correlation was found between amino-acetone excretion and that of either porphobilinogen or coproporphyrin.

ENZYMATIC DEACYLATION OF S35-BENZYLPENICILLIN

Pruess, David L. (University of Wisconsin, Madison), and Marvin J. Johnson. Enzymatic deacylation of S(35)-benzylpenicillin. J. Bacteriol. 90:380-383. 1965.-S(35)-benzylpenicillin, penicilloic acid, and penilloic acid were deacylated by cell suspensions of Escherichia coli and Micrococcus roseus. Both cultures deacylated penicillin most rapidly and penilloic acid least rapidly. The deacylase activity of M. roseus against penicilloic acid was cell-bound, probably requiring a metal ion for activity.