Donald Yamashiro

The synthesis and opiate activity of β-endorphin

Abstract The synthesis of the untriakontapeptide β-endorphin is described. The synthetic peptide is shown to possess opiate activity comparable with that of the natural product by the opiate receptor binding assay.

β-Endorphin: Structure-activity relationships in the guinea pig ileum and opiate receptor binding assays

Abstract The opiate activities of some derivatives and enzymatic digests of camel and human β-endorphin were determined in the guinea pig ileum and rat brain opiate receptor binding assays. Derivatives of β-endorphins altered within the amino-terminal five residues showed pronounced losses in activity. Anisylation of the C-terminal glutamic acid residue of βh-endorphin produced only small reductions in activity. Chymotryptic digestion greatly weakened the opiate activities of βh-endorphin, whereas carboxypeptidase A, tryptic and leucine aminopeptidase digests showed only small losses in potency. The C-terminus of β-endorphin appears to contribute little directly to opiate activity. Amino acid analysis and assay of the leucine aminopeptidase digests suggest that the larger potency of β-endorphin relative to Met-enkephalin may be a consequence of its greater resistance to exopeptidase attack.

β-Endorphin: Complete primary structure is required for full analgesic activity

Abstract The synthesis of βh-endorphin-(1–30) has been accomplished by the solid-phase procedure and its analgesic potency was assayed by the tail-flick method. Results showed that the synthetic analog had only 56% activity of the parent molecule. Thus, the complete sequence of 31 amino acid residues in βh-EP is required for full analgesic activity.

Synthesis of a peptide with full somatostatin activity.

Abstract A peptide has been synthesized according to the structure proposed for somatostatin by the solid phase method. The synthetic product was assayed and found to possess full somatostatin activity as compared with the natural material.

Determination of locust AKH-I by radioimmunoassay and the identification of an AKH-like factor in the locust brain

The N-terminal glutamic acid analog of the decapeptide locust adipokinetic hormone-I, [Glu1]AKH-I, was prepared by solid-phase synthesis and derivatized to [4-hydroxyphenyl propionyl-Glu1]AKH-I. This derivative was radioiodinated on the 4-hydroxyphenyl function ([125I]AKH analog). [Glu1]AKH-I was coupled to bovine serum albumin to produce rabbit antiserum. This, together with the [125I]AKH analog was utilized to develop a highly selective radioimmunoassay procedure (RIA) for detecting AKH-I in locusts. Methanol extracts of locust brain contain two factors (BI and BII) that inhibit protein synthesis in excised fat body tissue of vitellogenic female locusts. BI also elicits lipid mobilization when injected into adult male locusts. The HPLC retention time of BI on an RP-18 column is identical to that of locust adipokinetic hormone (AKH-I), both synthetic and derived from adult corpora cardiaca (CC). The second brain factor (BII) does not exhibit lipid mobilizing activity. One tissue-equivalent of BI contains 33 ng of AKH-I as determined by RIA, compared to 450 ng native HPLC-separated AKH-I in locust CC.

[D-Thr2, Thz5]- and [D-Met2 ,Thz5]-enkephalinamides: potent analgesics by intravenous injection.

Abstract Two enkephalin analogs, [D-Met 2 , Thz 5 ]-enkephalinamide and [D-Thr 2 , Thz 5 ]-enkephalinamide, have been synthesized by the solid-phase method. When injected centrally, [D-Thr 2 , Thz 5 ]-enkephalinamide is 3.5 times more potent than the [D-Met 2 , Thz 5 ] analog. However, the two are equipotent and 4.2–4.8 times more potent than morphine when injected intravenously.

Synthetic insulin-like growth factor II

Human insulin-like growth factor II with 67 amino acid residues and three disulfide bridges has been synthesized by the solid-phase method. Homogeneity of the synthetic product is ascertained by chromatofocusing, high performance liquid chromatography and amino acid analysis. In both radioimmunoassay and radioreceptor assay, the synthetic product is indistinguishable from the natural hormone.

β-Endorphin-(1–27): Acetylation of alpha-amino groups enhances immunoreactivity but diminishes analgesic and receptor-binding activities with no changes in circular dichroism spectra

Four synthetic βh-endorphin analogs have been assessed for their immunoreactivity, receptor-binding activity and analgesic potency as well as their α-helical content by circular dichroism. These synthetic analogs are: βh-endorphin-(1–27), [Gln8]-βh-endorphin-(1–27), [Ac-Tyr1]-βh-endorphin-(1–27) and [Ac-Tyr1, Gln8]-βh-endorphin-(1–27). Results show that acetylation caused 3.8–8.8 X increase of immunoreactivity in comparison with the parent analog but abolished receptor-binding and analgesic activities. In addition, acetylation does not alter circular dichrois spectra in 90% methanol. Thus, there is no correlation of α-helix content with biological activities of these four synthetic βh-endorphin analogs.

Isolation and properties of ovine [1-pyroglutamic acid]-β-lipoprotein

Abstract A new form of ovine β-lipotropin has been isolated by partition chromatography on agarose gel. All the evidence is consistent with the conclusion that its structure is identical to that of ovine β-lipotropin with the exception that the glutamic acid residue in position 1 was replaced by a pyroglutamic acid residue. Its lipolytic activity in isolated rabbit fat cells was about one-half that of β-lipotropin.

β-endorphin: Replacement of glutamic acid in position 8 by glutamine increases analgesic potency and opiate receptor-binding activity

Summary A β-endorphin analog with replacement of glutamic acid in position 8 by glutamine has been synthesized by modified procedures of the solid-phase method. The analgesic potency of the synthetic analog was increased to nearly three-fold with a concomitant increase of opiate receptor-binding activity in neuroblastoma × glioma hybrid cells. This is the first instance in which a replacement of a single amino acid causes an increase of analgesic potency of β-endorphin.