Preliminary work on a crude in vitro system for glutamic-γ-semialdehyde
synthesis in Escherichia coli has been described. The
cell extract synthesis of GSA is inhibited by proline; other allosteric
characteristics observed include sigmoidal substrate variation and
inhibition plots of activity. The membrane fraction and a low molecular
weight compound in...
An enzyme system from cell-free yeast homogenates mediating the
transfer of the methyl group from S-adenosylmethionine-methyl-C¹⁴
or methionine-methyl-C¹⁴ to C-28 of ergosterol has been studied.
The effects of divalent cations, suithydryl inhibitors and reducing
substances on the activity of the enzyme system have been investigated.
It was established that for...
The terminal reactions in the biosynthetic pathway of methionine
in Saccharomyces cerevisiae were investigated in this study. Analyses
of a number of methionine auxotrophs for biochemical deficiences
established four mutant groups. It was observed from qualitative feeding
experiments that some auxotrophs were able to utilize S-adenosylmethionine
(AM) and S-adenosyl-homocysteine (AH)...
The mechanism of transsulfuration and the role of cystathionine
in the biosynthesis of methionine in yeast were investigated.
Saccharomyces were shown to accumulate cystathionine by use
of the ³⁵S labeled compound.
Cell-free extracts of the wildtype clone as well as methionine
auxotrophs were shown to cleave cystathionine. The enzymatically
produced...
Studies were carried out to elucidate the mechanism of enzymatic
control of methionine biosynthesis in Saccharomyces cerevisiae.
Enzymatic studies demonstrated that, in addition to the methionine
activating enzyme, the S-adenosylmethionine:homocysteine
transmethylase enzyme was induced during cultivation in the presence
of excess methionine. A similar, though reduced effect was
observed when...
An attempt has been made to elucidate the biosynthetic precursor
of ethylene in the mold P. digitatum. By application of basic
radiotracer methodology and the utilization of several specifically
labeled radiochemical substrates, it has been possible to demonstrate
that the internal carbon atoms of C-4 dicarboxylic acids such
as succinate,...
Aseptic radiorespirometry has been used to examine
the utilization of external carbon sources by proliferating
Thiobacillus thioparus cells. These studies reveal
that glucose, galactose, mannose, fructose, ribose, DL-glutamate,
and L-aspartate were not utilized by this
chemoautotrophic organism. However, it has been shown
that trace amounts of acetate, glycine, DL-serine, DL-alanine,...
An enzyme system was prepared from Saccharomyces cerevisiae,
strain MCC, which carries out the transfer of the methyl group from
S-adenosylmethionine or methionine to the side chain of yeast sterols.
The cell-free system has been shown to be incapable of synthesizing
ergosterol but carries out the synthesis of two as...
Early studies on the biosynthesis of Sarubicin A, 1, had suggested the
intermediacy of the novel aromatic amino acid 6-hydroxyanthranilic acid,
17. To investigate the biosynthetic steps beyond 17, [¹³C-¹⁵N carboxamide]
6-hydroxyanthranilamide, 27a, was synthesized, and fed to fermentations
of Streptomyces helicus. Incorporation of 27a into 1 provided suggestive
evidence...
The continued propagation of antibiotic resistance requires the development of new therapeutics. The lipopeptide antibiotic enduracidin has demonstrated high activity against Gram-positive pathogens including methicillin-resistant Staphylococcus aureus. In addition to a lack of cross-resistance with existing antibiotic classes, enduracidin has no known transferrable resistance mechanism. The development of enduracidin as...
Molecular genetic and enzymological techniques have been employed to study antibiotic biosynthesis. The nonproteinogenic amino acid capreomycidine is the signature residue found in the tuberactinomycin family of antitubercular peptide antibiotics and an important element of the pharmacophore. Recombinant VioG, a single module peptide synthetase from the viomycin gene cluster cloned...
Molecular genetic and enzymological techniques have been employed to study antibiotic biosynthesis. In this thesis, we studied the formation and modification of the nonproteinogenic amino acid enduracididine (End), which exists in two important antibiotics, mannopeptimycins (MPPs) and enduracidin.
Sequence analysis of the MPP gene cluster revealed that the product of...
Molecular genetic and enzymological techniques have been employed to study secondary metabolite biosynthesis. These investigations have focused on two projects: the cloning and heterologous expression of biosynthetic gene clusters from unculturable marine organisms and the characterization of individual enzymes involved in the biosynthesis of the antifungal agent blasticidin S. The...
Halogenated monoterpene production by the red macroalga Octhodes secundiramea was studied-under different levels of nutrient, bromide, vanadium and light delivery. The key products formed were identified as myrcene, betaelemene, the Z and E isomers of l0-bromomyrcene, 3-chloro-10E-bromomyrcene, Apakaocthodene A, and isomers of chloromyrcene and dibromomyrcene. The proposed pathway begins with...
The isoprenoid pathway is one of the major biosynthetic pathways of secondary metabolites. Isoprenoids with a C₂₀ skeleton are known as diterpenoids and are derived from the common precursor, geranylgeranyl diphosphate (GGPP). This dissertation describes approaches to discover the diterpene synthase enzymes which provide the backbone structures for pleuromutilin and...
Among the myriad of naturally occurring bioactive compounds are the aminocyclopentitol-containing natural products that represent a family of sugar-derived microbial secondary metabolites, such as the antibiotics pactamycin, allosamidin, and trehazolin. Pactamycin, a structurally unique aminocyclitol antibiotic isolated from Streptomyces pactum, consists of a 5-membered ring aminocyclitol (cyclopentitol) unit, two aromatic...