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Biomedical subjects

L Miller

Publications and source records attributed to L Miller.

At least 487 records · Page 27Linked to original sources
PubMed1970

Mode of action of pectic enzymes. II. Further purification of exopolygalacturonate lyase and pectinesterase from Clostridium multifermentans.

Exopolygalacturonate lyase and pectinesterase from Clostridium multifermentans were purified 156-fold and 178-fold, respectively, by gel filtration chromatography on Sephadex G-200. The activities of both enzymes coincided in a single protein peak. Profiles of the two activities also coincided in diethylaminoethyl-cellulose chromatography and zonal centrifugation. These studies indicated that the esterase and the lyase were either complexed or similar molecular species. The former seems more probable because of the relatively high molecular weight. Both activities were most stable at pH 6.0. The esterase was inactivated rapidly at pH 5 or 7. Lyase preparations were freed of pectinesterase activity by heating for 30 min at 38 C and pH 7.0.

Calcium Chloride↗
PubMed1970

Similarities in the action patterns of exopolygalacturonate lyase and pectinesterase from Clostridium multifermentans.

Exopolygalacturonate lyase and pectinesterase from Clostridium multifermentans were assayed simultaneously in the same reaction mixture which contained a highly esterified pectin, polymethyl polygalacturonic acid methyl glycoside. Lyase is specific for unesterified galacturonide residues and cannot degrade this substrate in the absence of the esterase. The rate for esterase was twice the rate for lyase throughout the entire course of the combined reaction. Thus, the molar ratio of the two enzyme activities was the same since the product of the lyase is an unsaturated digalacturonic acid containing two free carboxyl groups. Since clostridial exopolygalacturonate lyase is known to degrade polygalacturonate in a linear manner beginning from the reducing ends of polygalacturonate chains, it was apparent that clostridial pectinesterase must hydrolyze methyl groups in highly esterified pectins with an action pattern similar to that of the lyase. Otherwise it would be impossible for the two enzyme rates to have corresponded on the basis of a 2:1 ratio.

Calcium Chloride↗
PubMed1970

Summation of responding maintained by fixed-interval schedules.

A light and tone were separately correlated with responding maintained by fixed-interval schedules, in which the level of responding varied continuously throughout the duration of the interval. Responding during the presence of the single stimuli and their compound was compared during the successive segments of the interval. The following results were obtained: (1) more responses were emitted during compounding than were emitted during either stimulus alone in all segments of the interval; (2) increases in the number of responses across the interval during compounding paralleled increases during single-stimulus presentations. The sum of the responses emitted during the single stimuli was similar to the number of responses emitted during compounding, suggesting that the response tendencies correlated with the single stimuli combined in a summative or additive fashion.

Journal Article↗