Problems of Quantities and Units in Enzymology

Abstract

A knowledge of the molecular structure of an enzyme makes it possible to characterize it by different types of ‘amount’: number (of elementary entities), mass, volume, and amount of substance. Another type of amount is obtained by measuring the rate of reaction of a suitable substrate change elicited by the enzyme in a special defined assay mixture; this way of using the catalytic effect has lead international bodies to different definitions of (kind of) quantity and unit. Their problems are discussed. A coherent scheme of the most important kinds of quantities employed by the enzymologist is presented. The dangers of converting results with one type of assay method to those of another are explained.

Sialic Acid in Human Serum and Cerebrospinal Fluid. Comparison of methods and reference values

“…The presence of l mmol/1 (0.5 mmol/1) of some interfering compounds influenced the reaction of N-acetylneuraminic acid ( The results of 249 determinations pn sera from ostensibly healthy adults ranged from 1.53 mmol/1 (472 mg/1) to 3.15 minol/i (975 mg/1) and displayed an approximate Gaussian distribution in the histogram ( fig. According to the proposal of Dybkaer (29) we calculated the 0.025-0.50-0.975-reference intervals to be 1. According to the proposal of Dybkaer (29) we calculated the 0.025-0.50-0.975-reference intervals to be 1.…”

Η Κυτταροπλασματικη L-Α-Γλυκερο-3-Φωσφορικη Αφυδρογοναση (Sn-Γλυκερο- Λη-3-Φωσφορικον Οξυ: Nad+ 2-Οξειδοαναγωγαση E.C. 1.1.1.8.) Των Ερυθροκυτταρων

“…Έν τούτοις τό "katal" δέν είναι πολλαπλάσιον της IU, διότι αμφότερα έχουν διάφορον τύπον ορισμού, αί άριθμητικαί ο μως τιμαί τών αποτελεσμάτων της "ποσότητος τοϋ ενζύμου" είς IU, είναι ανάλογοι προς τήν "καταλυτικήν ποσότητα" είς. kat (Dybkaer 1975). 'Επίσης ή I.U.B.…”