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Biomedical subjects

M H Gold

Publications and source records attributed to M H Gold.

At least 109 records · Page 6Linked to original sources
PubMed1989

Characterization of a cDNA encoding a manganese peroxidase, from the lignin-degrading basidiomycete Phanerochaete chrysosporium.

A cDNA clone of a manganese peroxidase (MnP) from Phanerochaete chrysosporium was isolated and characterized. The cDNA contains 1314 nucleotides excluding the poly(A) tail and the coding region has 68% G + C content. The deduced mature MnP protein contains 357 amino acids and is preceded by a 21-amino acid leader sequence. The experimentally determined N-terminal sequence of the purified MnP-1 protein, pI = 4.9, corresponds to the deduced N-terminal sequence of the gene. The Mr of the mature MnP-1 deduced from the cDNA is 37,439, which is approximately 81.4% of the experimentally determined molecular weight. The difference is due to glycosylation and a single potential N-glycosylation site with the general sequence Asn-X-Thr/Ser is present in the deduced MnP-1 sequence. Consistent with the peroxidase mechanism of MnP, the proximal histidine, the distal histidine, and the distal arginine are all conserved and regions flanking these residues display homology with other peroxidases. Northern blot analysis indicates that MnP expression is controlled by nutrient nitrogen at the level of transcription. Southern blot hybridization analysis suggests that MnP-1 is a member of a family of MnP genes.

Amino Acid Sequence↗
PubMed1989

Manganese peroxidase from the lignin-degrading basidiomycete Phanerochaete chrysosporium. Transient state kinetics and reaction mechanism.

Stopped-flow techniques were used to investigate the kinetics of the formation of manganese peroxidase compound I (MnPI) and of the reactions of MnPI and manganese peroxidase compound II (MnPII) with p-cresol and MnII. All of the rate data were obtained from single turnover experiments under pseudo-first order conditions. In the presence of H2O2 the formation of MnPI is independent of pH over the range 3.12-8.29 with a second-order rate constant of (2.0 +/- 0.1) x 10(6) M-1 s-1. The activation energy for MnPI formation is 20 kJ mol-1. MnPI formation also occurs with organic peroxides such as peracetic acid, m-chloroperoxybenzoic acid, and p-nitroperoxybenzoic acid with second-order rate constants of 9.7 x 10(5), 9.5 x 10(4), and 5.9 x 10(4) M-1 s-1, respectively. The reactions of MnPI and MnPII with p-cresol strictly obeyed second-order kinetics. The second-order rate constant for the reaction of MnPII with p-cresol is extremely low, (9.5 +/- 0.5) M-1 s-1. Kinetic analysis of the reaction of MnII with MnPI and MnPII showed a binding interaction with the oxidized enzymes which led to saturation kinetics. The first-order dissociation rate constants for the reaction of MnII with MnPI and MnPII are (0.7 +/- 0.1) and (0.14 +/- 0.01) s-1, respectively, when the reaction is conducted in lactate buffer. Rate constants are considerably lower when the reactions are conducted in succinate buffer. Single turnover experiments confirmed that MnII serves as an obligatory substrate for MnPII and that both oxidized forms of the enzyme form productive complexes with MnII. Finally, these results suggest the alpha-hydroxy acids such as lactate facilitate the dissociation of MnIII from the enzyme.

Basidiomycota↗
PubMed1989

Evaluation and treatment of patients with human bite marks.

Physicians and other health care workers who care for patients who have sustained human bite marks need a working protocol to ensure that these patients receive proper care. This protocol involves taking a thorough history and performing a physical examination, approximately determining the bite mark age, and administering proper therapy. The history will help to determine whether a criminal act has been committed and which agencies need to be notified. The American Board of Forensic Odontology published criteria for bite mark analysis in 1984 that included a description of the bite mark including its size, shape, and color, along with techniques for collection of evidence from both the victim and suspect. To determine bite mark age, tissue response to injury (inflammation, granulation tissue formation, and matrix formation and remodeling) is reviewed. Finally, the bacteria that are found in these wounds and the proper use of antimicrobial agents are expanded upon.

Anti-Bacterial Agents↗
PubMed1989

Hereditary benign telangiectasia.

We describe a father and two daughters with hereditary benign telangiectasia. Both girls had numerous telangiectases distributed over the upper limbs, trunk, face, and vermilion border of the lips. The father displayed less extensive lesions and had been unaware of their presence. All three patients were in good health; the younger daughter had a past history of mild recurrent epistaxis. Differentiation of this benign entity from other primary telangiectatic disorders is discussed.

Adolescent↗
PubMed1989

Transformation by Complementation of an Adenine Auxotroph of the Lignin-Degrading Basidiomycete Phanerochaete chrysosporium.

Swollen basidiospores of an adenine auxotroph of Phanerochaete chrysosporium were protoplasted with Novozyme 234 and transformed to prototrophy by using a plasmid containing the gene for an adenine biosynthetic enzyme from Schizophyllum commune. Transformation frequencies of 100 transformants per mug of DNA were obtained. Southern blot analysis of DNA extracted from transformants demonstrated that plasmid DNA was integrated into the chromosomal DNA in multiple tandem copies. Analysis of conidia and basidiospores from transformants demonstrated that the transforming character was mitotically and meiotically stable on both selective and nonselective media. Genetic crosses between double mutants transformed for adenine prototrophy and other auxotrophic strains yielded Ade progeny, which indicated that integration occurred at a site(s) other than the resident adenine biosynthetic gene.

Journal Article↗
PubMed1989

Human bite marks. Differential diagnosis.

Human bite marks are common findings in cases of fights among children, child abuse, sexual abuse, among institutionalized persons, and in a number of homicide cases. Human bites can mimic annular or arciform dermatoses. These are reviewed from both a clinical and histologic viewpoint. An example is presented of a 2 year-old girl with several annular lesions that were clinically mistaken for a dermatophyte infection. Antifungal medications were ineffective. After several days, a dermatologist identified the lesions as human bites. Physicians and other health care workers must be able to differentiate the clinical appearance of bite marks from other dermatologic diseases at an early stage so as to initiate proper therapy and counseling and, if indicated, a search for the perpetrator.

Bites and Stings↗
PubMed1988

Spectroscopic and kinetic properties of the oxidized intermediates of lignin peroxidase from Phanerochaete chrysosporium.

Stopped-flow rapid scan techniques were used to obtain a spectrum of nearly homogeneous lignin peroxidase compound I (LiPI) under pseudo-first order conditions at the unusually low pH optimum (3.0) for the enzyme. The LiPI spectrum had a Soret band at 407 nm with approximately 60% reduced intensity and a visible maximum at 650 nm. Under steady-state conditions a Soret spectrum for lignin peroxidase compound II (LiPII) was also obtained. The Soret maximum of LiPII at 420 nm was only approximately 15% reduced in intensity compared to native LiP. Transient state kinetic results confirmed the pH independence of LiPI formation over the pH range 3.06-7.39. The rate constant was (6.5 +/- 0.2) x 10(5) M-1 S-1. Addition of excess veratryl alcohol to LiPI resulted in its reduction to LiPII with subsequent reduction of LiPII to the native enzyme. Reactions of LiPI and LiPII with veratryl alcohol exhibited marked pH dependencies. For the LiPI reaction the rate constants ranged from 2.5 x 10(6) M-1 S-1 at pH 3.06 to 4.1 x 10(3) M-1 S-1 at pH 7.39; for the LiPII reaction, 1.6 x 10(5) M-1 S-1 (pH 3.06) to 2.3 x 10(3) M-1 S-1 (pH 5.16). These single turnover experiments demonstrate directly that the pH dependence of these reactions dictates the overall pH dependence of this novel enzyme. These results are consistent with the one-electron oxidation of veratryl alcohol to an aryl cation radical by LiPI and by LiPII.

Agaricales↗
PubMed1988

Manganese peroxidase from the basidiomycete Phanerochaete chrysosporium: spectral characterization of the oxidized states and the catalytic cycle.

Manganese peroxidase (MnP), an extracellular heme enzyme from the lignin-degrading fungus Phanerochaete chrysosporium, catalyzes the Mn(II)-dependent oxidation of a variety of phenols. Herein, we spectroscopically characterize the oxidized states of MnP compounds I, II, and III and clarify the role of Mn in the catalytic cycle of the enzyme. Addition of 1 equiv of H2O2 to the native ferric enzyme yields compound I, characterized by absorption maxima at 407, 558, 605, and 650 nm. Addition of 2 or 250 equiv of H2O2 to the native enzyme yields compound II or III, respectively, identified by absorption maxima at 420, 528, and 555 nm or at 417, 545, and 579 nm, respectively. These characteristics are very similar to those of horseradish peroxidase (HRP) and lignin peroxidase (LiP) compounds I, II, and III. Addition of 1 equiv of either Mn(II), ferrocyanide, or a variety of phenols to MnP compound I rapidly reduces it to MnP compound II. In contrast, only Mn(II) or ferrocyanide, added at a concentration of 1 equiv, reduces compound II. The Mn(III) produced by the enzymic oxidation of Mn(II) oxidizes the terminal phenolic substrates. This indicates that compounds I and II of MnP contain 2 and 1 oxidizing equiv, respectively, over the native ferric resting enzyme and that the catalytic cycle of the enzyme follows the path native enzyme----compound I----compound II----native enzyme. In addition, these results indicate that Mn(II) serves as an obligatory substrate for MnP compound II, allowing the enzyme to complete its catalytic cycle. Finally, the Mn(II)/Mn(III) redox couple enables the enzyme to rapidly oxidize the terminal phenolic substrates.

Basidiomycota↗
PubMed1988

Spectral characterization of manganese peroxidase, an extracellular heme enzyme from the lignin-degrading basidiomycete, Phanerochaete chrysosporium.

Manganese peroxidase (MnP) is a component of the lignin degradation system of the basidiomycetous fungus, Phanerochaete chrysosporium. This novel MnII-dependent extracellular enzyme (Mr = 46,000) contains a single protoporphyrin IX prosthetic group and oxidizes phenolic lignin model compounds as well as a variety of other substrates. To elucidate the heme environment of this enzyme, we have studied its electron paramagnetic resonance and resonance Raman spectroscopic properties. These studies indicate that the native enzyme is predominantly in the high-spin ferric form and has a histidine as fifth ligand. The reduced enzyme has a high-spin, pentacoordinate ferrous heme. Fluoride and cyanide readily bind to the sixth coordination position of the heme iron in the native form, thereby changing MnP into a typical high-spin, hexacoordinate fluoro adduct or a low-spin, hexacoordinate cyano adduct, respectively. EPR spectra of 14NO- and 15NO-adducts of ferrous MnP were compared with those of horseradish peroxidase (HRP); the presence of a proximal histidine ligand was confirmed from the pattern of superhyperfine splittings of the NO signals centered at g approximately equal to 2.005. The appearance of the FeII-His stretch at approximately 240 cm-1 and its apparent lack of deuterium sensitivity suggest that the N delta proton of the proximal histidine of the enzyme is more strongly hydrogen bonded than that of oxygen carrier globins and that this imidazole ligand may be described as having a comparatively strong anionic character. Although resonance Raman frequencies for the spin- and coordination-state marker bands of native MnP, nu 3 (1487), nu 19 (1565), and nu 10 (1622 cm-1), do not fall into frequency regions expected for typical penta- or hexacoordinate high-spin ferric heme complexes, ligation of fluoride produces frequency shifts of these bands very similar to those observed for cytochrome c peroxidase and HRP. Hence, these data strongly suggest that the iron in native MnP is predominantly high-spin pentacoordinate. Analysis of the Raman frequencies indicates that the dx2-y2 orbital of the native enzyme is at higher energy than that of metmyoglobin. These features of the heme in MnP must be favorable for the peroxidase catalytic mechanism involving oxidation of the heme iron to FeIV. Consequently, it is most likely that the heme environment of MnP resembles those of HRP, cytochrome c peroxidase, and lignin peroxidase.

Basidiomycota↗
PubMed1988

Beta-blocking drugs and psoriasis. A review of cutaneous side effects and retrospective analysis of their effects on psoriasis.

beta-Adrenergic receptor blockers have been prescribed widely since their introduction 20 years ago. Noncardiac indications for beta-blockers have been expanded. Dermatologic manifestations of beta-blockers are reviewed in conjunction with their more liberal use. A retrospective analysis of our experience with beta-blockers in patients with psoriasis is presented. A 1-year study of 588 psoriatic patients who received treatment revealed that 26 patients were taking beta-blockers. Exacerbations of psoriasis were noted in 72.4% of these patients. beta-Blockers may worsen psoriasis and should be carefully evaluated in the management of these patients.

Adrenergic beta-Antagonists↗
PubMed1987

Lignin peroxidase: resonance Raman spectral evidence for compound II and for a temperature-dependent coordination-state equilibrium in the ferric enzyme.

Resonance Raman (RR) spectroscopy of lignin peroxidase (ligninase, dairylpropane oxygenase) from the basidiomycete Phanerochaete chrysosporium suggests two different coordination states for the native ferric enzyme. Evidence for a high-spin, hexacoordinate ferric protoporphyrin IX was presented by Andersson et al. [Andersson, L. A., Renganathan, V., Chiu, A.A., Loehr, T. M., & Gold, M. H. (1985) J. Biol. Chem. 260, 6080-6087], whereas Kuila et al. [Kuila, D., Tien, M., Fee, J. A., & Ondrias, M. R. (1985) Biochemistry 24, 3394-3397] proposed a high-spin, pentacoordinate ferric system. Because the two RR spectral studies were performed at different temperatures, we explored the possibility that lignin peroxidase might exhibit temperature-dependent coordination-state equilibria. Resonance Raman results presented herein indicate that this hypothesis is indeed correct. At or near 25 degrees C, the ferric iron of lignin peroxidase is predominantly high spin, pentacoordinate; however, at less than or equal to 2 degrees C, the high-spin, hexacoordinate state dominates, as indicated by the frequencies of well-documented spin- and coordination-state marker bands for iron protoporphyrin IX. The temperature-dependent behavior of lignin peroxidase is thus similar to that of cytochrome c peroxidase (CCP). Furthermore, lignin peroxidase, like horseradish peroxidase (HRP) and CCP, clearly has a vacant coordination site trans to the native fifth ligand at ambient temperature. High-frequency RR spectra of compound II of lignin peroxidase are also presented. The observed shifts to higher frequency for both the oxidation-state marker band v4 and the spin- and coordination-state marker band v10 are similar to those reported for the compound II forms of HRP and lactoperoxidase and for ferryl myoglobin.(ABSTRACT TRUNCATED AT 250 WORDS)

Basidiomycota↗
PubMed1987

Mating System and Basidiospore Formation in the Lignin-Degrading Basidiomycete Phanerochaete chrysosporium.

Prototrophic strains recovered from crosses between auxotrophic strains of the lignin-degrading basidiomycete Phanerochaete chrysosporium were induced to fruit. The progeny of most of these self-crosses were prototrophic, indicating that the nuclei of the original prototroph were wild-type recombinants rather than complementary heterokaryons and that the binucleate basidiospores of this organism are homokaryotic. Various wild-type strains were shown to have multinucleate cells lacking clamp connections and to possess a variable number of sterigmata per basidium. Colonies arising from single conidia of various wild-type strains were all capable of producing fruit bodies and basidiospores. In addition, single basidiospores from three wild-type strains all produced fruit bodies and basidiospores. Nonfruiting as well as fruiting isolates were obtained from single basidiospores of five other wild-type strains. Basidiospores from these fruiting isolates always yielded colonies that fruited, again indicating that the spores are homokaryotic. Nonfruiting isolates from the same strain did not produce basidiospores when allowed to form a heterokaryon, implying that these isolates do not represent mating types. All this evidence indicates that P. chrysosporium has a primary homothallic mating system. In addition to fruiting and nonfruiting phenotypes, basidiospores from strain OGC101, a derivative of ME-446, gave rise to colonies which did not grow on cellulose (Cel). The fruiting, nonfruiting, and Cel phenotypes differed from each other and from the parental wild-type strain in a variety of characteristics, including growth, conidiation, and evolution of CO(2) from C-side chain-labeled lignin, indicating that strain OCG101 is a heterokaryon.

Journal Article↗
PubMed1986

Mn(II) oxidation is the principal function of the extracellular Mn-peroxidase from Phanerochaete chrysosporium.

The manganese peroxidase (MnP), from the lignin-degrading fungus Phanerochaete chrysosporium, an H2O2-dependent heme enzyme, oxidizes a variety of organic compounds but only in the presence of Mn(II). The homogeneous enzyme rapidly oxidizes Mn(II) to Mn(III) with a pH optimum of 5.0; the latter was detected by the characteristic spectrum of its lactate complex. In the presence of H2O2 the enzyme oxidizes Mn(II) significantly faster than it oxidizes all other substrates. Addition of 1 M equivalent of H2O2 to the native enzyme in 20 mM Na-succinate, pH 4.5, yields MnP compound II, characterized by a Soret maximum at 416 nm. Subsequent addition of 1 M equivalent of Mn(II) to the compound II form of the enzyme results in its rapid reduction to the native Fe3+ species. Mn(III)-lactate oxidizes all of the compounds which are oxidized by the enzymatic system. The relative rates of oxidation of various substrates by the enzymatic and chemical systems are similar. In addition, when separated from the polymeric dye Poly B by a semipermeable membrane, the enzyme in the presence of Mn(II)-lactate and H2O2 oxidizes the substrate. All of these results indicate that the enzyme oxidizes Mn(II) to Mn(III) and that the Mn(III) complexed to lactate or other alpha-hydroxy acids acts as an obligatory oxidation intermediate in the oxidation of various dyes and lignin model compounds. In the absence of exogenous H2O2, the Mn-peroxidase oxidized NADH to NAD+, generating H2O2 in the process. The H2O2 generated by the oxidation of NADH could be utilized by the enzyme to oxidize a variety of other substrates.

Basidiomycota↗
PubMed1986

Role of molecular oxygen in lignin peroxidase reactions.

Homogeneous lignin peroxidase (diarylpropane oxygenase) oxidized veratryl alcohol to veratryl aldehyde under anaerobic conditions in the presence of either H2O2, m-chloroperoxybenzoic acid (mCPBA), or p-nitroperoxybenzoic acid (pNPBA). Lignin peroxidase also oxidized the 1-(3',4'-diethoxyphenyl)-1,2-dihydroxy-(4"-methoxyphenyl)-propane I under anaerobic conditions in the presence of mCPBA to yield 3,4-diethoxybenzaldehyde III and 1-(4'-methoxyphenyl)-1,2-dihydroxyethane IV. In contrast to what occurs under aerobic conditions, under anaerobic conditions no 2-hydroxy-1-(4'-methoxyphenyl)-1-oxoethane V was obtained. During the diarylpropane I cleavage under anaerobic conditions, 18O from H2(18)O was incorporated into the alpha-position of the phenylglycol IV. Lignin peroxidase also hydroxylated 1-(4'-ethoxy-3'-methoxyphenyl)propane II at the alpha-position to yield 1-(4'-ethoxy-3'-methoxyphenyl)-1-hydroxypropane VI under anaerobic conditions in the presence of mCPBA. During the phenylpropane II hydroxylation under anaerobic conditions, 18O from H2(18)O was incorporated into the alpha-position of VI. These results are rationalized according to a mechanism involving an initial one-electron oxidation of the diarylpropane I by the lignin peroxidase compound I to form a benzene pi cation radical which undergoes alpha, beta cleavage to produce a benzaldehyde and a C6C2 benzylic radical. The latter is then attacked by O2 to form a hydroperoxy radical which may decompose through a tetroxide to form the phenylglycol IV and phenylketol V. Under anaerobic conditions the C6C2 benzylic radical is probably oxidized to a carbonium ion which would be subsequently attacked by H2O to yield the phenylglycol V.

Anaerobiosis↗