Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A simple method for preparing plasma membranes from bovine testes is described. Bovine testicular receptor has a high affinity and specificity for 125I-labelled human FSH (follicle-stimulating hormone). The specific binding of 125I-labelled human FSH to the plasma membranes is a saturable process with respect to the amounts of receptor protein and FSH added. The association and dissociation of 125I-labelled human FSH are time- and temperature-dependent, and the binding of labelled human FSH to bovine testicular receptor is strong and not readily reversible. Scatchard [Ann. N.Y. Acad. Sci. (1949) 51, 660-672] analysis indicates a dissociation constant, Kd, of 9.8 X10(-11)M, and 5.9 X 10(-14)mol of binding sites/mg of membrane protein. The testicular membrane receptor is heat-labile. Preheating at 40 degrees C for 15 min destroyed 30% of the binding activity. Specific binding is pH-dependent, with an optimum between pH 7.0 and 7.5. Brief exposure to extremes of pH caused irreversible damage to the receptors. The ionic strength of the incubation medium markedly affects the association of 125I-labelled human FSH with its testicular receptor. Various cations at concentrations of 0.1M inhibit almost completely the binding of 125I-labelled human FSH. Nuclectides and steroid hormones at concentrations of 1mM and 5mu/ml respectively have no effect on the binding of FSH to its receptor. Incubation of membranes with and chymotrypsin resulted in an almost complete loss of binding activity, suggesting that protein moieties are essential for the binding of 125I-labelled human FSH. Binding of 125I-labelled human FSH to bovine testicular receptor does not result in destruction or degradation of the hormone.
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PMID:Properties of follicle-stimulating-hormone receptor in cell membranes of bovine testis. 24 18

The effects of various chemical and enzymatic treatments on the biological activity of porcine luteinizing hormone-releasing hormone (LH-RH) are described. This experiment was performed before the elucidation of the structure of LH-RH. LH-RH activity was abolished by the following endopeptidases: chymotrypsin, subtilisin, papain, and thermolysin, but not by pepsin or trypsin. Exopeptidases did not affect LH-RH activity, but a purified preparation of pyrolidone carbosylpeptidase did. The amino acid sequence of LH-RH/FSH-RH was established to be (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-Amine. This decapeptide lacks both the Amine terminus and the COOH terminus. Its Amine-terminal dipeptide sequence,(pyro)Glu-His, is similar to that of tyrotropin-releasing hormone. The lack of inactivation by the exopeptidases is in good agreement with these findings. Treatment with various chemical reagents showed that tyrosine, histidine, tryptophan, and arginine in LH-RH are important for its biological activity. Nitrous acid and Edman degradation did not inactivate LH-RH. These results are also in agreement with the determined structure of LH-RH. This hormone showed a high follicle-stimulating hormone-releasing hormone (FSH-RH) activity. The inactivation of LH-RH was always accompanied by a loss of FSH-RH activity. These experiments also shed some light on the structure-activity relationship of this hormone.
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PMID:Studies on the properties of hypothalamic luteinizing hormone-releasing hormone. 494 14