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T T Hai

Publications and source records attributed to T T Hai.

12 recordsLinked to original sources
PubMed1994

Diaspirin crosslinked hemoglobin (DCLHb) polymerization.

By employing proprietary polymerization agents possessing specific binding groups and by completing diaspirin crosslinked hemoglobin (DCLHb) polymerization under specific conditions, we have selectively achieved the following objectives: (1) the P50 was adjusted to the physiologic range or left- or right-shifted; (2) the surface of DCLHb was modified ("decorated"); (3) DCLHb was polymerized but not decorated; (4) DCLHb was polymerized and decorated; or (5) DCLHb was site-specifically modified and polymerized.

Amino Acids, Diamino↗
PubMed1986

Isozyme-specific enzyme inhibitors. 10. Adenosine 5'-triphosphate derivatives as substrates or inhibitors of methionine adenosyltransferases of rat normal and hepatoma tissues.

Monosubstituted adenosine 5'-triphosphate (ATP) derivatives with a substituent of up to four atoms at any of eight positions in the adenosine moiety, or with an isosteric group replacement at O5' or in the triphosphate moiety, have been evaluated kinetically as substrates and inhibitors of liver (I), kidney (II), and Novikoff hepatoma (T) variants of rat methionine adenosyltransferase. Inhibitory potencies were expressed as KM(ATP)/Ki (for competitive inhibition vs. ATP) or as KM(ATP)/KM when no Ki value was available. Variant I was inhibited more powerfully than II or T by all of four ATP derivatives for which comparative data were obtained. Among 15 ATP derivatives, four were substrates of II or T and the remainder inhibited II and T competitively with respect to ATP; most derivatives exhibited at least moderate (greater than 0.5) inhibitory potency. Differential inhibition of II and T was shown by 11 of 14 ATP derivatives; relative inhibitory potencies (T:II) ranged from 5.5 with 2-SCH3-ATP [KM(ATP)/Ki = 1.3 with T] to 0.24 with the ATP isostere with a C5'-CH2-P alpha system [KM(ATP)/Ki = 1.9 with II]. The most effective inhibitor was the P beta, P gamma imido isostere of ATP with inhibitory potencies of 25 and 35 for II and T, respectively. The findings provide further evidence that substrate derivatives with single short groups attached at various positions, or with single isosteric group replacements, are frequently useful probes in the design of isozyme-selective inhibitors.

Adenosine Triphosphate↗
PubMed1986

Isozyme-specific enzyme inhibitors. 11. L-homocysteine-ATP S-C5' covalent adducts as inhibitors of rat methionine adenosyltransferases.

The title compounds (14a,b) were 5' epimers of a derivative of a phosphonate isostere of ATP in which the CH2OP alpha system of ATP was replaced by CH(R)CH2P alpha [R = L-S(CH2)2CH(NH2)CO2H]. They resisted synthesis via attempted S-alkylation of the corresponding epimeric 5'-mercapto derivatives. A practicable route to 14a,b commenced with Michael condensation of L-homocysteine with the diphenyl ester of the 5',6'-vinyl phosphonate analogue of 2',3'-O-isopropylideneadenosine 5'-phosphate. The resulting epimeric 5' thioethers were separated by reverse-phase HPLC. The two phenyl groups were replaced by benzyl groups, after which the alpha-amino acid residue was protected as an N-Boc methyl ester. Both benzyl groups were removed by hydrogenolysis, and the resulting phosphonic acid was converted into its pyrophosphoryl derivative. Blocking groups were then removed under conditions that furnished 14a and 14b without racemization of their L-amino acid residues. Also synthesized were the P beta-NH-P gamma imido analogue (15a) of 14a and the sulfoxide derivative (16a) of 14a. The structures of 14a and 16a were verified by FAB mass spectra, which revealed the protonated molecular ions of their sodium salts. All adducts appeared to function as dual substrate site inhibitors (competitive to ATP and to methionine) of the rat normal tissue (MAT-2) form of methionine adenosyltransferase (MAT); 14a and 15a [KM(ATP)/Ki = 4 and 9, respectively] were the most effective. Adduct 15a was the most effective inhibitor [KM(ATP)/Ki = 13] of the MAT-T form from rat hepatoma tissue; the kinetic data indicated dual-site inhibition by 15a with apparently complete coverage of the ATP site and incomplete coverage of the methionine site. The inhibition properties of the adducts indicated little preference in the order in which the two MAT forms bound ATP and methionine.

Adenosine Triphosphate↗
PubMed1986

Isozyme-specific enzyme inhibitors. 12. C- and N-methylmethionines as substrates and inhibitors of methionine adenosyltransferases of normal and hepatoma rat tissues.

The 2-, 3-, and 4-mono-C-methyl derivatives of D,L-methionine (Met) have been resolved into the 10 possible enantiomeric forms having the configurations 2-Me-D, 2-Me-L, 3(alpha or beta)-Me-D, 3(alpha or beta)-Me-L, 4(alpha or beta)-Me-D, and 4(alpha or beta)-Me-L (the alpha designation was given to enantiomeric pairs that had higher Rf values on silica gel chromatograms than their diastereomeric counterparts). All compounds were weak, poorly selective inhibitors of the rat M-2 (normal tissue) and M-T (Novikoff ascitic hepatoma) variants of Met adenosyltransferase. Kinetic analysis of the three most effective showed them to be competitive inhibitors with respect to Met with both variants; the strongest inhibition (KM(Met)/Ki = 0.03) was that of M-T by 3 beta-Me-L-Met. The Me-Met enantiomers had low substrate efficiencies (Vmax/KM) in the range (0.5-2.2) X 10(-4) that of L-Met with M-2 (0.2-1.3) X 10(-3) with M-T among seven compounds studied. At a 4 mM level, seven of the enantiomers were converted to adenosylmethionine derivatives more rapidly by M-T than by M-2. Among these, 2-Me-L-Met, 3 alpha-Me-L-Met, 3 alpha-Me-D-Met, and 4 beta-Me-D-Met had little or no substrate activity with M-2. These differences in substrate specificity are potentially exploitable in the design of compounds with selective toxicity for rat tumor tissue. N-Me- and N-(n-Bu)-Met, and the Met analogue in which NH is substituted for S, were weak inhibitors of M-T and M-2 and showed no substrate activity at a level of 4 mM.

Animals↗
PubMed1982

Use of adenine nucleotide derivatives to assess the potential of exo-active-site-directed reagents as species- or isozyme-specific enzyme inactivators. 3. Synthesis of adenosine 5'-triphosphate derivatives with N6- or 8-substituents bearing iodoacetyl groups.

Several series of N6- or 8-substituted derivatives of adenosine 5'-triphosphate (ATP) were synthesized. N6-(omega-Aminoalkyl) derivatives of adenosine 5'-monophosphate (AMP) were converted into their omega-N-carbobenzyloxy derivatives, and these were converted, via the 2',3'-O-carbonyl derivatives of their 5'-phosphorimidazolidates, into the corresponding ATP derivatives. Hydrogenolytic removal of the carbobenzyloxy groups, followed by iodoacetylation of the omega-amino groups with N-(iodoacetoxy)succinimide, gave N6-R-ATP, where R = (CH2)nNHCOCH2I (n = 2--8) or (CH2)nCON)CH3)(CH2)mN(CH3)CO(CH2)nNHCOCH2I (n = m = 3; n = 3, m = 4; n = 4, m = 3; n = m = 4). Condensation of N6-(omega-aminoalkyl) derivatives of AMP with N-hydroxysuccinimide esters of omega-[N-(carbobenzyloxy)amino] carboxylic acids gave N6-(CH2)nNHCO(CH2)mNH-Cbz derivatives of AMP which, upon conversion to the corresponding derivatives of ATP, followed by removal of the carbobenzyloxy group and iodoacetylation, as described above, gave N6-(CH2)nNHCO(CH2)mNHCOCH2I-ATP derivatives (n = 3, m = 5 or 6; n = 4, m = 5; n = 6, m = 1--6). The same sequence of reactions starting with N6-[omega-(methylamino)alkyl] derivatives of N6-CH3-AMP gave N6-CH3, N6-(CH2)nH(CH3)CO(CH2)mNHCOCH2I derivatives of ATP (n = 4, m = 3, 5 or 6; n = 6, m = 5 or 6). Reaction of alpha, omega-diaminoalkanes with 8-Br-ATP gave 8-NH(CH2)nNH2 derivatives of ATP, which upon iodoacetylation gave 8-NH(CH2)nNHCOCH2I derivatives of ATP (n = 2, 4, 6, or 8). Substrate and inhibitor properties indicated that the ATP derivatives are potential exco-ATP-site-directed inactivators of hexokinases, adenylate kinases, and pyruvate kinases.

Adenosine Diphosphate↗
PubMed1982

Use of adenine nucleotide derivatives to assess the potential of exo-active-site-directed reagents as species- or isozyme-specific enzyme inactivators. 5. Interactions of adenosine 5'-triphosphate derivatives with rat pyruvate kinases, Escherichia coli thymidine kinase, and yeast and rat hexokinases.

Adenosine 5'-triphosphate (ATP) derivatives of the types N6-R-ATP [R = (CH2)nNHCOCH2I, (CH2)nNHCO-(CH2)mNHCOCH2I, or (CH2)nCON(Me)(CH2)mN(Me)CO(CH2)nNHCOCH2I], N6-Me-N6-R-ATP [R = (CH2)nN-(Me)CO(CH2)mNHCOCH2I], and 8-R-ATP [R = NM(CH2)nNHCOCH2I] with 5--19 spacer atoms between N6 or C-8 and iodine have been evaluated as potential exo-ATP-site-directed reagents for phosphokinases. Substrate and inhibitor properties indicated that the compounds possessed affinity for the ATP sites of the muscle (M), kidney (K), and liver (L) isozymes of rat pyruvate kinase (PK), of E. coli thymidine kinase (TK), and of yeast hexokinase (HK) and rat KH I, II, and III isozymes. Tests for time-dependent loss of enzyme activity (inactivation) were performed under conditions in which a large proportion of each phosphokinase was present as an enzyme-inhibitor complex. No ATP-site-directed inactivations resulted when the M, L, or K isozymes of PK were exposed for 8 h, 22 degrees C, to 5 mM levels of 18 ATP derivatives or 6 analogous ADP derivatives or when yeast HK or rat KH I, II, or III was exposed for 6 h, 22 degrees C, to 5 mM levels of 28 ATP derivatives. Escherichia coli TK was inactivated by 6 of 25 ATP derivatives tested at 10 mM, 6 h, 0 degrees C; inactivation was slowed by MgATP in the case of N6-CH3-N6-R-ATP [R = (CH2)4N(CH3)CO(CH2)5NHCOCH2I]. Only 1% of 298 enzyme-inhibitor combinations exhibited ATP-site-directed inactivation, signifying that few suitably positioned and sufficiently reactive nucleophilic groups were present near the enzymic ATP sites. Studies have now shown that exo-active-site-directed reagents can act as isozyme- or species-selective enzyme inhibitors. The present survey indicates that in many cases such reagents may be difficult of access when data are not available regarding structural or physicochemical features of the target enzyme adjacent to its catalytic site.

Adenosine Triphosphate↗
PubMed1982

Species- or isozyme-specific enzyme inhibitors. 6. Synthesis and evaluation of two-substrate condensation products as inhibitors of hexokinases and thymidine kinases.

Syntheses are described of p1-(adenosine-5')-p3-(glucose-6) triphosphate (Ap3 glucose), Ap4 glucose, and p1-(adenosine-5')-P3-(thymidine-5') triphosphate (Ap3T). The compounds were not substrates of any of the enzymes used in the present studies. Ap3 glucose and Ap4 glucose were inhibitors of yeast hexokinase (HK) and the rat isozymes HK I-III; in general, they had less affinity for the enzymes than the substrates ATP and glucose. Inhibition constants (Ki values) of Ap3T with rat mitochondrial thymidine kinase (M-TK) and rat cytoplasmic TK (C-TK) were determined for variable thymidine (TdR) with a constant saturating level of ATP and for variable ATP with constant saturating TdR. Ap3T was a potent and selective inhibitor of M-TK [KM (TdR)/Ki = 1.6, KM (ATP)/Ki = 38 with variable ATP; KM (TdR) Ki = 0.06, KM (ATP)/Ki = 1.4 with variable TdR] relative to C-TK [KM (TdR)/Ki = 0.006, KM (ATP)/Ki = 0.7 with variable ATP; KM (TdR)/Ki = 0.001, KM (ATP)/Ki = 0.12 with variable TdR]. Inhibition of M-TK and C-TK by Ap3T differed qualitatively and quantitatively from inhibition under the same conditions by the metabolic feedback inhibitor TdR 5'-triphosphate.

Animals↗
PubMed1982

Species- or isozyme-specific enzyme inhibitors. 7. Selective effects in inhibitions of rat adenylate kinase isozymes by adenosine 5'-phosphate derivatives.

Monosubstituted derivatives of adenosine 5'-phosphate (AMP) with substituents of 1-3 atoms or group replacements at any of 11 positions have been synthesized and examined as substrates and inhibitors of the rat muscle adenylate kinase isozyme (AK-M), and the rat AK II and III isozymes predominant in poorly differentiated hepatoma tissue and normal liver tissue, respectively. Inhibition indexes of the compounds were expressed as KM (AMP)/Ki for competitive inhibition or as KM (AMP)/KM when only KM was available. Substituents at N(1), N6, or C(8) or on ionizable phosphate oxygen reduced inhibition below measurable levels; 2'-deoxy-AMP and adenosine 5'-sulfate had identical inhibition indexes with all three isozymes; compounds with substituents at C(2), O(2'), O(3'), C(4'), C(5'), or O(5') had higher inhibition indexes with AK-M than with AK II or III and the same or similar indexes for AK II and III. The most effective and/or selective inhibitors were 2-NHMe-AMP (index with AK-M, 0.2; index ratio, AK-M/AK III, 9.1), 2'-O-Me-AMP (index with AK-M, 0.14; index ratio, AK-M/AK III, 8.2), 2',3'-O-CMe2-AMP (index with AK-M, 0.25; index ratio, AK-M/AK II, 6.6), 4'-allyl-AMP (index with AK-M, 0.97; index ratio, AK-M/AK III, 8.1), and 5'(S)-Et-AMP (index with AK-M, 0.64; index ratio, AK-M/AK II, 11.2). The study provides additional evidence that the attachment of simple substituents to various atoms in turn of a substrate is a potentially useful approach in early stages of the attempted design of isozyme-selective inhibitors.

Adenosine Monophosphate↗
PubMed1982

Species- or isozyme-specific enzyme inhibitors. 9. Selective effects in inhibitions of rat pyruvate kinase isozymes by adenosine 5'-diphosphate derivatives.

Derivatives of adenosine 5'-diphosphate (ADP) with a substituent of 1-4 atoms at any of eight positions have been synthesized and evaluated as substrates and inhibitors of the liver (L), muscle (M), and kidney (K) isozymes of rat pyruvate kinase (PK). Inhibitory potencies of the compounds were expressed as KM (ADP)/Ki or as KM (ADP)/KM when no Ki value was available. Nine of 14 ADP derivatives exhibited differential inhibitions. The M and K isozymes, which cross-react immunologically with each other but not with the L form, were inhibited differentially by 5 of the 14 derivatives. PK-K was preferentially inhibited by two derivatives, PK-L by three derivatives, and PK-M by two derivatives. Among the most selective and/or effective inhibitors were 3'-OMe-ADP [KM (ADP)/Ki = 0.07 with PK-K; inhibitory potency, K/M/L, 7.6:6.0:1], N6-Me,N6-(CH2)4N(Me)COMe-ADP (prepared previously) [KM (ADP)/KM = 0.43 with PK-L; inhibitory potency, L/K/M, 3:2:1], and 8-NHEt-ADP [KM (ADP)/Ki = 1.0 with PK-M; inhibitory potency, M/K/L, 7.1:1.2:1]. These and previous studies with two other enzymes indicate that monosubstituted substrate derivatives that bear short substituents (usually 1-4 atoms) at various positions are potentially useful probes in early stages of the attempted design of isozyme-selective inhibitors.

Adenosine Diphosphate↗
PubMedDate not supplied

Synthesis of water-soluble, nonimmunogenic polyamide cross-linking agents.

Novel polyamides were developed that can be used as cross-linking agents for proteins such as hemoglobin. Water-soluble, nonimmunogenic polyamides containing oxygen and sulfur atoms in the backbone were prepared by the polycondensation of the diacids bis(carboxymethyloxyacetyl)-1,4-diaminobutane (1a) or 3, 3'-thiodipropionic acid (1b) with diethylene glycol bis(3-aminopropyl) ether (2). The resulting alpha,omega-diacids were converted to the corresponding activated esters using any of a variety of carboxylic acid activating reagents including the novel reagent diphenyl(1-methylimidazol-2-thiyl)phosphonate (9). The resulting polyamides could be activated with a broad spectrum of groups that allow for the cross-linking and surface modification of proteins.

Chromatography, Gel↗