Phosphorus-containing enzymes

Wagner-Jauregg T, Hackley BE, Lies TA et al. (1955). Model reactions of phosphorus-containing enzyme inactivators. IV. The catalysis of certain metal salts and chelates in the hydrolysis of diisopropyl fluo-rosphate. J Am Chem Soc, 77, 922-929. 

This enzyme system catalyzes the oxidation of various nitrogen-, sulfur -, and phosphorus-containing compounds, which tend to be nucleophilic, although compounds with an anionic group are not substrates. For example, the N-oxidation of trimethylamine (Fig. 4.19) is catalyzed by this enzyme, but also the hydroxylation of secondary amines, imines, and arylamines and the oxidation of hydroxylamines and hydrazines ... 

This key enzyme of the nervous system is inactivated irreversibly by powerful phosphorus-containing poisons that had been developed as insecticides and as war gases (nerve gases, Box 12-C). Around 1949, the nerve gas diisopropylfluorophosphate (DFP) was shown also to inactivate chymotrypsin. When radioactive 32P-containing DFP was allowed to react the 32P became... 

Casein is not coagulated by heat. It is precipitated by acids and by rennin. a proteolytic enzyme obtained from the stomach or calves. Casein is a conjugated protein belonging lo the group uf phosphoproteins. The enzyme trypsin can hydrolyze off a phosphorus-containing peptone. 

The following classes of phosphorus-containing compounds were not affected by large amounts of the enzyme with Mg2+, Mn2+, Zn2+, or Co2+ at either pH 9.1 or 7.5 (1) ribo- or deoxyribonucleoside mono-, di-, or triphosphates (2) ribo- or deoxyribopolynucleotides (3) nucleotide coenzymes (e.g., DPN+, UDP-glucose) (4) phosphomonoesters (e.g., glucose-6-P, p-nitrophenyl phosphate) (5) cyclic tri- or tetrametaphos-phates (6) phosphorofluoridates (inorganic phosphorofluoridate, adenosine 5 -phosphorofloridate) and (7) phosphonates (e.g., methylene-bis-phosphonate) (12, 57). 

In 1978 Cohn and Hu (1) demonstrated the isotopic effect by 180 on the Ip-nmr spectrum of inorganic phosphate. For each that replaces an 1 0, an upfield shift of 0.021 ppm results. Thus the chemical shift for HP O 58 is 0.084 ppm downfield from Hpl 04=. Based on this observation it is obvious that any chemical event that potentially involves substitution or exchange of an 0 for 16() in phosphorus containing compounds can be followed by monitoring the Ip-nmr spectrum throughout the course of the reaction. This article describes experiments from my laboratory on two enzymes that catalyze phosphoryl transfer reactions and our use of the [1 0/1 0] lp-nmr methodology to detect intermediates in the enzymic reactions. 

Takeda, 1998). Under iron-replete conditions, the silicon and nitrogen uptake is roughly equal, while under low-iron conditions diatoms exhibit Si/N uptake ratios of 3. Under low iron concentrations the suppression of iron-containing enzymes such as nitrate or nitrite reductase has been confirmed for the chain-forming diatoms in the laboratory (de Baar et aL, 2000), resulting in reduced uptake of nitrogen relative to phosphorus and N/P ratios of 4-6 as compared to —12-14 at adequate iron supply. 

They observed specific inactivation of the B1 subunit of the E. coli enzyme, the production of free base and chloride, the irreversible modification of protein sulfhydryl groups, and the formation of a new chromophoric absorbance at 320 nm. The tyrosyl radical was not quenched following inactivation, and in this original report a new phosphorus-containing sugar was observed and tentatively identified as 2-deoxyribose 5-diphosphate. Furthermore, inactivation with [ C1]-, [a- P]-, or [5- H]ClCDP did not lead to radiolabeled protein. 

Specific choline esterase develops its max activity at pH 7 and at low levels OF acetylcholine (less than 2.5 mg %). Both enzymes are inhibited by very small quantities of physostig-mine (eserine). Acetylcholinesterase is inhibited by phosphorus-containing insecticides and nerve gases. 

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