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Biomedical subjects

M Knight

Publications and source records attributed to M Knight.

At least 109 records · Page 6Linked to original sources
PubMed1973

Measurement of methaemalbumin in plasma.

Using the method of Chong and Owen (1967), the normal range of methaemalbumin in plasma was 0 to 0.6 mg/100 ml, expressed as milligrams of haematin per cent. Previous results, using the method of Shinowara and Walters (1963), reported a normal range of 0 to 8.0 mg/100 ml, but it was expressed as milligrams of haemoglobin percent. The conversion factor from the Shinowara method is as follows: mg haematin % = mg haemoglobin % x 0.04.

Heme↗
PubMed1972

The bacterial oxidation of picolinamide, a photolytic product of Diquat.

The pathway of oxidation of picolinamide (pyridine-2-carboxamide) by a Gram-negative rod has been elucidated. Under conditions of high pH, restricted aeration and high substrate concentration, whole cells released 2,5-dihydroxypyridine into culture supernatants. Sodium arsenite at 5mm caused whole cells to accumulate 6-hydroxypicolinate, and, at 1mm, pyruvate, in culture media. Whole cells oxidized picolinamide, picolinate, 6-hydroxypicolinate, maleamate and maleate without lag. Cell-free extracts converted picolinamide into picolinate, and hydroxylated picolinate to 6-hydroxypicolinate. The hydroxylase was particulate, but could be solubilized by ultrasonic treatment; it required NAD(+) for activity, and did not require molecular oxygen. 2,5-Dihydroxypyridine was converted into maleamate and formate by an oxygenase requiring GSH and Fe(2+). Maleamate was deamidated to maleate, and maleate isomerized to fumarate, by unsupplemented extracts.

Amides↗
PubMed1972

The bacterial oxidation of N-methylisonicotinate, a photolytic product of paraquat.

Two bacteria have been isolated that are capable of oxidizing N-methylisonicotinate, a photodegradation product of Paraquat (1.1'-dimethyl-4,4'-bipyridylium ion). N-Methylisonicotinate-grown cells of strain 4C1, a Gram-positive rod, oxidized 2-hydroxy-N-methylisonicotinate without lag. Cell-free extracts of these cells converted 2-hydroxyisonicotinate into 2,6-dihydroxyisonicotinate; the reaction did not require molecular oxygen. Maleamate was deamidated and maleate isomerized to fumarate by soluble enzyme systems. [(14)C]Formaldehyde was isolated as the dimedone derivative from the supernatant of a cell suspension oxidizing N-[(14)C]methylisonicotinate, and no [(14)C]-methylamine was detected. Whole cells incubated with N-methyl[carboxy-(14)C]isonicotinate released 95% of the radioactivity as (14)CO(2). The second bacterium, strain 4C2, a Gram-negative rod, did not oxidize any of the mono- or di-hydroxypyridines or their N-methyl derivatives that were available or could be synthesized; nor did cell-free extracts oxidize any of these compounds. Methylamine was oxidized by whole cells without lag; cell-free extracts converted methylamine into formaldehyde when a soluble enzyme system requiring an electron acceptor was used; formaldehyde was oxidized to formate and formate to CO(2) by enzyme systems requiring NAD(+).

Bacteria↗
PubMed1972

A heat-stable nicotinamide-adenine dinucleotide glycohydrolase from Pseudomonas putida KB1. Partial purification and some properties of the enzyme and an inhibitory protein.

A thermostable NAD(P)(+) glycohydrolase (EC 3.2.2.6) detected in cell-free extracts of Pseudomonas putida KB1 was purified to a single component on polyacrylamide-gel electrophoresis. A heat-labile inhibitor of the enzyme was also partially purified. Enzyme free of inhibitor is present in culture supernatants. After an ultrasonic treatment enzyme-inhibitor complex and excess of inhibitor are present in both the cell-debris and soluble fractions. The general properties of the enzyme and inhibitor are described. The molecular weights of enzyme, inhibitor and enzyme-inhibitor complex, determined by gel filtration are about 23500, 15000 and 35000 respectively. The binding of inhibitor and enzyme is inhibited by the presence of substrate.

Cell-Free System↗
PubMed1966

The synthesis of amino acids by Methanobacterium omelianskii.

1. Methanobacterium omelianskii was grown on (14)CO(2) and unlabelled ethanol, or on [1-(14)C]- or [2-(14)C]-ethanol and unlabelled carbon dioxide. The cell protein was hydrolysed and certain of the amino acids were isolated and degraded. 2. Carbon from both carbon dioxide and ethanol is used for biosynthesis of amino acids, and in most cases ethanol is incorporated as a C(2) unit. Ethanol carbon atoms and carbon dioxide carbon atoms apparently enter the same range of compounds. Ethanol and carbon dioxide are equally important as sources of cell carbon. 3. The origins of carbon atoms of aspartate, alanine, glycine, serine and threonine are consistent with the synthesis of these amino acids, by pathways known to exist in aerobic organisms, from pyruvate arising by a C(2)+C(1) condensation. The proportion of total radioactivity found in C-1 of lysine, proline, methionine and valine is consistent with synthesis of these amino acids by pathways similar to those found in Escherichia coli. Isoleucine is probably formed by carboxylation of a C(5) precursor formed entirely from ethanol. Glutamate is formed by an unknown pathway.

Amino Acids↗