Trimethyl Acetate Research Articles

Kinetic properties of the alpha-lytic protease of Sorangium sp., a bacterial homologue of the pancreatopeptidases.

The kinetics under consideration are those of a bacterial serine protease with the same "active serine" sequence as chymotrypsin, trypsin, and elastase, and with a single histidine residue in a sequence which closely matches the sequences around histidine-57 of chymotrypsin and the analogous histidine residues of trypsin and elastase. In agreement with previous evidence of an elastase-like specificity, esters of N-substituted, neutral, aliphatic L-amino acids proved to be good to excellent substrates for the α-enzyme; esters of arginine, tyrosine, and tryptophan were not hydrolyzed. The enzyme has a much higher activity than the pancreatopeptidases towards p-nitrophenyl acetate and p-nitrophenyl trimethyl acetate; the catalytic rate coefficient kc for the latter substrate is about fivefold greater than that of elastase.The catalytic properties match those of the pancreatopeptidases in the following respects. As demonstrated with N-acetyl-L-valine methyl ester as substrate, kc is dependent on an ionization with a pKa of 6.7 in water and 7.3 in H22O; Δ log (kc/Km)/ΔpH for this ionization is equal to 1.0; kc is reduced 50% when H2O is replaced by H22O. These findings are consistent with a requirement for a single unprotonated histidine residue and general basic catalysis by that residue. The burst of p-nitrophenol in hydrolyses of p-nitrophenyl trimethyl acetate is proportional to [E]0; the magnitude of the proportionality factor and the rate of attainment of a steady state are consistent with the condition [Formula: see text], as in chymotrypsin kinetics. Thus the purely catalytic properties of the α-enzyme match those of chymotrypsin very closely. These findings do not support reaction mechanisms which require two catalytically functional histidine residues for such catalysis. The substrate-binding properties of the α-enzyme differ from those of chymotrypsin in that substrate binding does not depend on ionization of an N-terminal α-amino group; Km for the hydrolysis of N-acetyl-L-valine methyl ester is constant from pH 5 to pH 10 and enzymatic activity is unaffected by acetylation of the enzyme's α- and ε-amino groups. Ks for the hydrolysis of p-nitrophenyl trimethyl acetate is appreciably greater than the Ks of elastase for this substrate.The chloromethyl ketones of glycine and valine did not inhibit the enzyme or alkylate its histidine residue.

INTRA-ARTICULAR INJECTIONS OF HYDROCORTISONE ACETATE, PREDNISOLONE TRIMETHYL ACETATE, AND METHYLPREDNISOLONE; A COMPARATIVE STUDY.

INTRA-ARTICULAR INJECTIONS OF HYDROCORTISONE ACETATE, PREDNISOLONE TRIMETHYL ACETATE, AND METHYLPREDNISOLONE: A COMPARATIVE STUDY Get access K. HINGORANI, K. HINGORANI Department of Physical Medicine, Dryburn HospitalDurham Search for other works by this author on: Oxford Academic PubMed Google Scholar A. ZINOVIEFF A. ZINOVIEFF Department of Physical Medicine, Dryburn HospitalDurham Search for other works by this author on: Oxford Academic PubMed Google Scholar Rheumatology, Volume 7, Issue 8, November 1964, Pages 299–303, https://doi.org/10.1093/rheumatology/7.8.299 Published: 01 November 1964

Intra-Muscular Prednisolone Trimethyl Acetate Therapy Experience in its Use and Complications

Intra-Muscular Prednisolone Trimethyl Acetate Therapy Experience in its Use and Complications

9-Alpha-fluorohydrocortisone alone and combined with hydrocortisone in the management of chronic adrenal insufficiency.

SINCE the advent of cortisone in 1949, replacement therapy in chronic adrenal insufficiency has reached a more optimal level than had heretofore been possible. Cortisone acetate has been used alone and in combination with sodium chloride, as well as with various preparations of desoxycorticosterone. Thorn and his associates (1) have had extensive experience in the use of cortisone and of desoxycorticosterone in pellet form or as the trimethyl ester. For maintenance therapy they recommend cortisone in a dosage of 15 to 30 mg. daily together with desoxycorticosterone trimethyl acetate, 25 mg. every three weeks. We have been able to maintain our Addisonian patients on an average of 37.5 mg. of cortisone daily by mouth (given in three doses), with the addition of 4 to 6 grams of enteric-coated sodium chloride (2). The use of cortisone combined with desoxycorticosterone has been necessary only in 2 totally adrenalectomized patients in whom our usual replacement regimen did not correct the postural hypotension.