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Biomedical subjects

H Minakata

Publications and source records attributed to H Minakata.

At least 73 records · Page 4Linked to original sources
PubMed1993

Structure and function of the molluscan myoactive tetradecapeptides.

Effects of myoactive tetradecapeptides, Achatina excitatory peptide 2 and 3 (AEP2 and AEP3) and Fusinus excitatory peptide 4 (FEP4), on several molluscan muscles and neurons were investigated. In the penis retractor and radula retractor muscles of Achatina fulica (pulmonate), the three peptides enhanced the tetanic contraction elicited by nerve stimulations. The order of potency was AEP2 > AEP3 > FEP4, although the effects of AEP3 and FEP4 on the radula retractor were somewhat irregular. AEP2 also induced rhythmic bursts of activity in the buccal ganglionic neuron B4 known as a cholinergic motoneuron of the radula retractor. In the radula protractor and retractor muscles of Fusinus ferrugineus (prosobranch), FEP4 was most potent in enhancing the contraction. The enhancement was greater in the protractor than in the retractor. It was suggested that myoactive tetradecapeptides modulate mainly the cholinergic transmission in molluscan muscles.

Amino Acid Sequence↗
PubMed1992

Effect of the D-Phe2 residue on molecular conformation of an endogenous neuropeptide achatin-I. Comparison of X-ray crystal structures of achatin-I (H-Gly-D-Phe-Ala-Asp-OH) and achatin-II (H-Gly-Phe-Ala-Asp-OH).

The molecular conformation of achatin-II neutral form (H-Gly-Phe-Ala-Asp-OH), an endogenous peptide from the Achatina fulica ganglia, was elucidated by X-ray crystal analysis. The molecule takes an extended beta-pleated structure stabilized by 5 intermolecular hydrogen bonds with the antiparallely arranged molecules. This is in contrast with the turn conformation of a neuroactive achatin-I (H-Gly-D-Phe-Ala-Asp-OH) [(1992) FEBS Lett. 276,95-97]. The conformational comparison of both of the molecules makes clear the structural role which D-Phe residue of achatin-I plays in forming a definite active form.

Amino Acid Sequence↗
PubMed1992

The FMRFamide-related decapeptide of Mytilus contains a D-amino acid residue.

1. An FMRFamide-related decapeptide isolated from the anterior byssus retractor muscle (ABRM) of the bivalve mollusc, Mytilus edulis, was shown to have D-Leu as the second amino acid residue. 2. The excitatory effects of the peptide (Mytilus-FFRFamide) on the ABRM were not changed appreciably by substituting an L-Leu residue for the D-Leu residue.

Animals↗
PubMed1992

Crystal structure and molecular conformation of achatin-I (H-Gly-D-Phe-Ala-Asp-OH), an endogenous neuropeptide containing a D-amino acid residue.

In order to investigate the active conformation of achatin-I (H-Gly-D-Phe-Ala-Asp-OH), an endogenous neuropeptide from the Achatina fulica ganglia, its crystal structure and molecular conformation were analysed by the X-ray diffraction method. Crystals from methanol/dioxane are monoclinic, space group P2(1) with a = 5.083(1), b = 9.125(1), c = 20.939(3) A, beta = 94.73(1) degrees. The structure was solved by direct methods and refined to R = 0.051 for 1714 independent reflections with /Fo/ greater than sigma (Fo). The molecule exists as a zwitterion with the Gly N-terminal end protonated and Asp beta-carboxyl deprotonated; the C-terminal of Asp is in a neutral state. The molecule takes a kind of beta turn structure with the D-Phe-Ala residues at the corner of the bend. This turn conformation is primarily formed by the strong intramolecular hydrogen bonds of NH(Gly)...O delta 1 (Asp) and NH(Asp)...O delta 1 (Asp) pairs, thus forming a 15-membered ring structure. Judging from the published data concerning the structure-activity relationship, this turn conformation may reflect an important feature related to the neuroexcitatory activity of achatin-I.

Amino Acid Sequence↗
PubMed1992

Amino acid sequences of trypsin inhibitors from oriental pickling melon (Cucumis melo L. var. Conomon Makino) seeds.

Three inhibitors (CMCTI-I, II, and III) were isolated from oriental pickling melon (Cucumis melo L. var. Conomon Makino) seeds by acetone precipitation, gel filtration, and reversed phase chromatography. The amino acid sequences of these inhibitors were: [table; see text] The reactive sites (P1 and P1' sites) of these inhibitors are presumed to be the Lys-Ile indicated by an arrow, comparing them with other squash family inhibitors. All three inhibitors can inhibit lysyl endopeptidase and trypsin at the enzyme-inhibitor ratio of 1:1.

Amino Acid Sequence↗
PubMed1992

Mytilus-inhibitory peptide analogues isolated from the ganglia of a pulmonate mollusc, Achatina fulica.

1. Ten peptides that showed an inhibitory effect on phasic contraction of the ABRM of Mytilus were isolated from the ganglia of the African giant snail, Achatina fulica. 2. Seven of the peptides were shown to be hexapeptides having -Pro-Xaa-Phe-Val-NH2 as a common structure, which was previously shown to be a characteristic of Mytilus inhibitory peptides (MIPs). 3. The remaining three were pentadecapeptides, each of which consisted of two MIP-related hexapeptides linked by -Gly-Arg-Arg-.

Amino Acid Sequence↗
PubMed1992

Achatin-I, an excitatory neurotransmitter having a D-phenylalanine residue of Achatina giant neurones.

The neuroexcitatory peptide isolated from Achatina ganglia was identical to the synthetic Gly-D-Phe-L-Ala-L-Asp with respect to either the bioassay experiments using the Achatina neurones or the instrumental analysis (1H-NMR, SIMS, CD and HPLC). We termed it achatin-I (yield: 50 micrograms from 30,000 animals). Its stereoisomer, Gly-L-Phe-L-Ala-L-Asp, termed achatin-II, was also isolated from the ganglia (yield: 17 micrograms), but this was ineffective on the Achatina neurones. Of the eight possible stereoisomers, only achatin-I markedly showed excitatory effects on the two Achatina neurones, PON and TAN, and [D-Ala3] achatin-I (Gly-D-Phe-D-Ala-L-Asp) had the slight effects. Among the fourteen neurones tested, seven, including the two mentioned above, were excited by achatin-I, whereas no neurone was inhibited. Achatin-I produced an inward current (Iin) with an increase in the membrane conductance (g) under voltage clamp. ED50 of achatin-I for exciting the neurones were 0.20-1.47 x 10(-5) M, and its Emax were 6.33-5.02 nA. Of the achatin-I analogues examined, only the three, Gly-Gly-D-Phe-L-Ala-L-Asp, D-Phe-L-Ala-L-Asp and Gly-D-Phe-L-Ala-L-Asn, produced Iin, but much smaller than that of achatin-I. The equiactive molar ratios (EMRs) of the four effective related peptides (three analogues and a stereoisomer) vs. achatin-I were: 8-60 for Gly-Gly-D-Phe-L-Ala-L-Asp, 200 - > 250 for D-Phe-L-Ala-L-Asp and > 200 for Gly-D-Phe-L-Ala-L-Asn and Gly-D-Phe-D-Ala-L-Asp. The Iin induced by achatin-I was blocked under the /Na+/0-free state, but unaffected under the [Ca2+]-free (replaced with Co2+), [Cl-]0-free or [K+]-enriched (3.0 x) medium, indicating that the Iin is produced by the gNa increase of neuromembrane. We propose that achatin-I having a D-phenylalanine residue is an excitatory neurotransmitter of the Achatina neurones.

Action Potentials↗
PubMed1991

Fulicin, a novel neuropeptide containing a D-amino acid residue isolated from the ganglia of Achatina fulica.

A novel pentapeptide containing a D-amino acid residue was purified from the central ganglia of the African giant snail Achatina fulica Ferussac, and it was named fulicin. The primary structure of the peptide was determined to be Phe-D-Asn-Glu-Phe-Val-NH2. Fulicin potentiated tetanic contraction of the penis retractor muscle of this snail at very low concentrations, and also showed modulatory actions on the activity of the buccal and ventricular muscles and the central ganglionic neurons.

Amino Acid Sequence↗
PubMed1991

Purification of achatin-I from the atria of the African giant snail, Achatina fulica, and its possible function.

Achatin-I previously purified from the ganglia of the African giant snail Achatina fulica was isolated from the atria of this snail. Achatin-I appeared to enhance the cardiac activity in two ways; centrally this peptide increased impulse frequency and produced spike broadening of the identified heart excitatory neuron, PON, and peripherally it enhanced amplitude and frequency of the heart beat. Achatin-I showed excitatory actions not only on the heart but on several other muscles.

Amino Acid Sequence↗
PubMed1991

APGW-amide as an inhibitory neurotransmitter of Achatina fulica Ferussac.

APGWamide (L-Ala-L-Pro-Gly-L-Trp-NH2) was purified from the ganglia of an African giant snail (Achatina fulica Ferussac). This peptide inhibited (hyperpolarized) more than half of the Achatina neurone types tested. This produced an outward current with the membrane conductance increase of RAPN (right anterior pallial neurone) under voltage clamp. The ED50 of the peptide was 6.2 x 10(-6) M (95% confidence limit: 5.0-7.8 x 10(-6) M) and the Emax was 3.9 +/- 0.2 nA. The effects were due to a membrane permeability increase to K+. The peptide is proposed as an inhibitory neurotransmitter of the Achatina neurones.

Animals↗
PubMed1991

Slow inward current induced by achatin-I, an endogenous peptide with a D-Phe residue.

Following a preliminary report on the isolation of a neuroactive tetrapeptide, achatin-I (Gly-D-Phe-L-Ala-L-Asp) that has a D-phenylalanine residue, from the Achatina fulica ganglia, the pharmacological features of this peptide on Achatina giant neurones were now worked out in detail. Of the eight possible stereoisomers, only achatin-I markedly, and [D-Ala3]achatin-I slightly, induced a slow inward current (Iin) with an increase in membrane conductance (g) of the identifiable neurones, tonically autoactive neurone (TAN), dorsal-right cerebral distinct neurone (d-RCDN) and periodically oscillating neurone (PON) which had been tested previously. Of 23 types of neurones tested, 10 types including the three mentioned were excited by achatin-I, whereas no neurone was inhibited. The ED50 of achatin-I for the neurones tested were 0.2-2.7 x 10(-5) M, and that for PON was the lowest. The Hill coefficients of achatin-1. 0.62-0.80, derived from 1.0 Emax values of achatin-I for producing Iin, 4.2-6.3 nA, were significantly greater than those of [D-Ala3]achatin-I, 1.8-3.4 nA. Iin of TAN and d-RCDN induced by achatin-I was blocked in the Na(+)-free state, but unaffected in the Ca2(+)-free (replaced with Co2+), Cl(-)-free or K(+)-enriched (3.0X) state, indicating that the current was produced by the g increase in response to Na+. However, the Iin was partially blocked by tetrodotoxin 10(-4) M. We propose that achatin-I is an excitatory neurotransmitter on Achatina neurones.

Amino Acid Sequence↗
PubMed1991

Structure-activity relationship studies on the endogenous neuroactive tetrapeptide achatin-I on giant neurons of Achatina fulica Ferussac.

The structure-activity relationships of achatin-I, a neuroactive peptide containing a D-phenylalanine residue, for producing excitatory effects on three different types of Achatina neurons, PON, TAN and d-RCDN, were studied under the voltage clamp method. Of the peptides examined, only Gly-Gly-D-Phe-L-Ala-L-Asp (IV). D-Phe-L-Ala-L-Asp (V) and Gly-D-Phe-L-Ala-L-Asn (XVI) produced an inward current with increased membrane conductance similar to achatin-1 (I). The structure-activity relationship was essentially the same for the three Achatina neuron types. The equiactive molar ratios (EMRs) of the active peptides vs. achatin-I (I) were calculated from their dose-response curves: 8 - 60 for Gly-Gly-DPhe-L-Ala-L-Asp (IV), 200 - greater than 250 for D-Phe-L-Ala-L-Asp (V) and greater than 200 for Gly-D-Phe-L-Ala-L-Asn (XVI). These values indicate that the achatin-I receptor in the Achatina neurons is highly structure-specific.

Amino Acid Sequence↗