Hideo Okai

Transesterification of oil by fatty acid-modified lipase

Fatty acid was covalently attached to lipase (EC 3.1.1.3.) fromPhycomyces nites, yielding a modified lipase of higher specific activity in hydrolytic and synthetic reactions in organic solvents. Attached long-chain fatty acids solubilized the lipase in organic solvent and, therefore, promotion of dispersibility in organic solvent resulted in much higher reactivity. The initial rate of transesterification by modified lipase was almost 40 times that of native lipase in organic solvent. The specificities and selectivity of the modified lipase depended on the kind of attached fatty acid.

Bitter Taste of Synthetic C-Terminal Tetradecapeptide of Bovine β-Casein, H-Pro196-Val-Leu-Gly-Pro-Val-Arg-Gly-Pro-Phe-Pro-Ile-Ile-Val209-OH, and Its Related Peptides

The primary structure of bovine β-casein contains the partial sequence of -Pro196-Val-Leu-Gly-Pro-Val-Arg-Gly-Pro-Phe-Pro-Ile-Ile-Val209 in the C-terminal portion. We previously reported that the synthetic C-terminal octapeptide, Arg202-Val209, is extremely bitter with its threshold value 0.004 mm, 250 times as strong as that of caffeine. To further investigate the bitter taste of the C-terminal portion of β-casein, we synthesized the C-terminal tetradecapeptide, Pro196-Val209, and some of its fragments. A hydrophobic hexapeptide, Pro196-Val201, was twice as bitter as caffeine. The bitter taste of the decapeptide, Pro200-Val209, was the same as that of Arg202-Val209. Although the tetradecapeptide, Pro196-Val209, was composed of two bitter peptides, Pro196-Val201 and Arg202-Val209, its bitter taste was weaker than that of Arg202-Val209 and its threshold value was 0.015 mm. We suggested that the increase of bitterness in peptides through the introduction of hydrophobic amino acids depended on the number of ...

Synthesis of 2-acetamido-1-N[N-(tert-butoxycarbonyl)-l-aspart-1-oyl-(l-phenylalanyl-l-serine methyl ester)-4-oyl]-2-deoxy-β-d-glucopyranosylamine and analogs

Abstract 2-Acetamido-1- N -[ N -( tert -butoxycarbonyl)- l -aspart-1-oyl-( l -phenylalanyl- l -serine methyl ester)-4-oyl]-2-deoxy-β- d -glucopyranosylamine and analogs containing d -glucopyranosyl, 4- O -β- d -glucopyranosyl- d -glucopyranosyl, l -Phe- l -Ala, and d -Phe- l -Ser were synthesized by condensation of glycosylamines having free hydroxyl groups with tripeptide esters activated with N -hydroxysuccinimide.

Variation in Bitterness Potency When Introducing Gly-Gly Residue into Bitter Peptides

We previously reported that Gly-Gly-Arg-Pro and Arg-Pro-Gly-Gly, the derivatives of a bitter peptide Arg-Pro, had no bitterness although Gly-Arg-Pro and Arg-Pro-Gly had a bitter taste at the same level as that of Arg-Pro. To elucidate the mechanism of elimination of bitterness by the introduction of the Gly-Gly residues, we synthesized Gly-Gly derivatives of other bitter peptides such as Phe-Phe, Val-Val-Val, and Arg-Pro-Phe-Phe, and examined the effectiveness of Gly-Gly residues in eliminating bitterness. We suggest that, for Arg-Pro and Val-Val-Val, the Gly-Gly residue might prevent a hydrophobic group from binding to a taste receptor.

Syntheses of Methyl 2,3-di-O-Glycyl-α-D-glucopyranoside and 4,6-di-O-Glycyl-2,3-di-O-methyl-α-D-glucopyranoside, and Removal of Aminoacyl Groups from Sugar Moieties

Abstract To confirm the potential usefulness of amino acid residues as protecting groups for sugar hydroxyls, methyl 2,3-di-O-glycyl-α-D-glucopyranoside (5) and methyl 4,6-di-O-glycyl-2,3-di-O-methyl-α-D-gluco-pyranoside (7) were synthesized as reference compounds. Conditions were then established for the removal of these aminoacyl groups from the sugar molecules. The reference compounds were easily prepared by condensation of methyl α-D-glucopyranoside derivatives with N-protected glycine in the presence of dicyclohexyl-carbodiimide (DCC). The aminoacyl groups were removed by alkaline treatment, as were conventional acyl groups and also with ease by enzymatic hydrolysis using Pronase E. Conventional ester and ether protecting groups are not removed by such enzymatic treatment. Removal of aminoacyl group from sugar moieties on a practical scale is also described.

One Step Synthesis of Inverted Aspartame Type Sweetener, Ac-Phe-Lys, Using Chemically Modified Chymotrypsin.

To search for techniques of simplified peptide synthesis, benzyloxycarbonyl chymotrypsin was prepared by a water-soluble acylating reagent and used to make Ac-Phe-Lys, an artificial peptide sweetener, which was selected as a target compound. As a result of using chemically modified chymotrypsin, Lys can be coupled directly with Ac-Phe and Ac-Phe-Lys made virtually in one step. Moreover, the total yield from preparation and purification steps for Ac-Phe-Lys was 13%. The value corresponds to that of the chemical synthesis method. On the contrary, enzymatic synthesis using native chymotrypsin cannot reach the level of the new method. It is expected that the method is more effective for simplified peptide synthesis as compared with other methods, especially on a large scale.

Relationship between taste and structure of O-aminoacyl sugars containing basic amino acids

To study the relationship between taste and structure of O-aminoacyl sugars, a number of O-aminoacyl sugars containing basic amino acids were prepared. Taste quality of O-aminoacyl sugars was dependent on the side chain length of basic amino acids that were introduced into sugars. O-Aminoacyl sugars had an excellent sodium ion diet effect that could reduce sodium ion intake to 10%.

Reconstruction of peptide using p-dimethylsulfoniophenol ester in aqueous solution

Summaryp-Dimethylsulfoniophenol (DSP) ester was applied on the reconstruction of peptide, because its hydrophilicity was favorable for the reaction performed in aqueous media. As an example, the biological response of an enzymatically digested peptide hormone, Substance P (SP), was recovered by the reaction with pyroglutamyl (pGlu)-Phe-DSP. This result showed that pGlu-Phe-DSP restored the active site of SP destroyed by the enzyme.

Remarkably Enhanced Enantioselective Hydrolysis of Amino Acid Esters With Tripeptide Catalyst in Micellar Systems.

ミセル系(カチオン型:ヘキサデシルトリメチルアソモニウム=プロミド(CTAB),非イオン型:α-[4-(1,1,3,3一テトラメチルブチル)フェニル] -ω- ヒドロキシデカキス(オキシエチレン)(TritonX-100),ソルビタンのポリ(オキシエチレン)誘導体モノラウリン酸エステル(Tween20),α -テトラデシル -ω-ヒドロキシヘプタキス(オキシエチレン)(C14(EO)7),アニオン型:ドデシル硫酸ナトリウム(SDS))におけるトリペプチド触媒(N-ベソジルオキシカルボニル-L-フェニルアラニル-L-ヒスチジル-L-ロイシン)による長鎖基質(N-ドデカノイル-D及びL-フェニルアラニンのP-ニトロフェニルエステル)の不斉加水分解は,界面活性剤の濃度及び構造を変化させることで制御できることが明確となった.興味ある結果をまとめると:反応加速性について,(a)二次速度定数(ka, obsd)は,CMC付近で顕著に増大し,また,反応速度増大(カチオン型 >> 非イオン型 >> アニオン型)には,ミセルの頭部基が重要な役割を果たレていることが示された.一方,立体特異性に関して,(b)不斉選択性(kLa, obsd / kDa, obsd)は,すべてのミセル系においてL-体基質優先の反応性を示し,CMC以上では,ほぼ一定の値を示した.ミセルの頭部基は,不斉選択性の増大(非イオン型 > アニオン型 > カチオン型)にも重要な役割を果たしており,とくに,C14(EO)7ミセル系のCMC付近で顕著に大きな不斉選択性(L/D=77)を発現した.

Further Studies of l-Ornithyltaurine HCl, A New Salty Peptide

In 1984 our research group found that a series of basic dipeptides, such as H-L-Orn-Tau-OH · HCl [1] and others, possessed a salty state.